Skills in Fallout 2 are set at character creation based on the SPECIAL statistics the player chooses, and can be increased throughout the game using points that are rewarded when the player gains a level. Intelligence determines how many points are earned with each level, and the level of the skill determines how many points it costs to increase it. Between 0% and 100%, spending 1 point will cause a 1% raise in the skill. Between 101% and

Note: Upgraded versions of weapons have been excluded from the weapons lists for the sake of length.

Base Formula: 20% + (2 x CH)
Barter is usually considered a poor skill to tag due to the fact that money is plentiful, especially late in the game, due to the prices associated with weaponry taken from dead enemies. This skill effects how much merchants will charge for their goods, and how much they'll offer for yours. Outside of the barter interface it also effects how much the combat implant surgeries cost, as well as how much various merchants will ask in order to upgrade your weapons.

Big Guns
Base Formula: 10% + AG
Applies to: Avenger Minigun, Bozar, Flamer, Light Support Weapon, M60, Minigun, Rocket Launcher, Vindicator Minigun.
Big guns is a combat skill, meaning it affects your chance to hit, critical chance, and damage with the respective weapons. For big guns this means miniguns, flame throwers, and rocket launchers. Big guns appear in the middle of the game (assuming you follow an average progression), so tagging this skill can cause problems early on, but become rewarding in the end.

Base Formula: 15% + (PE + IN)/2
The doctor skill is very similar to the first aid skill, but it tends to heal more hit points each time it succeeds, and is capable of healing crippled limbs. Like first aid, the doctor skill can only be used a few times before the character is strained, however the character can use first aid even if they can no longer use doctor, and vice-versa. This skill can be used either through the skilldex (red button on the right end of the interface), by left clicking on a target and scrolling down to the pipboy face, or by using a related item held in your active item slot. Doctor can be worthwhile to tag if you plan on having party members, especially since it starts lower and is harder to raise than first aid. Note that your effective doctor skill can be boosted by 20% by having a doctor's bag in your active item slot, and 40% by having a paramedic's bag there. Using either a doctor's bag or paramedic's bag will eventually consume the item, but it takes quite a few uses.

Energy Weapons
Base Formula: 10% + AG
Applies to: Alien Blaster, Gatling Laser, Laser Pistol, Laser Rifle, Plasma Pistol, Plasma Rifle, Solar Scorcher, YK32 Pulse Pistol, YK42B Pulse Rifle.
Energy weapons is a combat skill, meaning it affects your chance to hit, critical chance, and damage with the respective weapons. Any ranged weapon that uses energy cells generally falls within this category. Tagging this skill could be problematic, as energy weapons only appear late in the game, though they are among the most deadly. This skill is a strong candidate for the Tag! perk, which allows the play to choose an additional tag skill later in the game.

First Aid
Base Formula: 30% + (PE + IN)
First aid is similar to doctor, though it tends to heal fewer hit points, and is unable to heal crippled limbs. First aid tends to work faster in terms of in-game time. It's notable that first aid can be raised (only up to 91% however) by reading first aid manuals that are scattered throughout the game. Your effective first aid skill can be boosted by 20% by having a first aid kit in your active item slot, and 40% by having a field medic's first aid kit there. Using either of these will eventually consume the item, but it takes quite a few uses. First aid is not worth tagging as doctor starts lower, is harder to raise, and cannot be raised by books.

Base Formula: 20% + (3 x LK)
This skill is used to determine if you win when you gamble at a slot machine, card table, or dice game. With a high enough skill, you will never lose, however endless free money is only so useful, especially later on when money is almost a non-issue. This is one of the skills that I recommend that no one tags, ever. On a side note, the locations where gambling is available are (in no specific order): The Den, Redding, and New Reno. There may be others, and if anyone knows of another location, please contact me.

Base Formula: 20% + (PE + AG)/2
Used for the opening of locked containers and doors, this skill can be incredibly useful. It is worth noting that an extremely low skill (or low luck score) can cause a player to jam the lock of the container or door they are trying to pick. Jammed locks will revert after several days, but it's a good idea to save before hand if your skill is low. There are two types of locks, traditional and electronic. Using your lockpicking skill without a lock pick will often work, but lock pick sets are plentiful and light. Using a light pick set or electric lock pick will give an effective +20% to your lock pick skill, while using an expanded lock pick set or electric lock pick MKII will give an effective +40% to your skill, in all cases it must be for the correct type of lock. Critical failures can occasionally destroy the pick used, aside from that occurrence lock picks are never consumed. I've found that using the lockpick skill on some doors (such as the doors in the Slavers' guild in the Den) can lock them, using lockpick sets works as well. This means you can use some doors to stop attackers, and in the case of the Slavers' guild, break up an otherwise very large number of enemies. Locking a door also yields 25 experience, however that door will not give any further experience for either locking or unlocking it again.

Melee Weapons
Base Formula: 55% + (AG + ST)/2
Applies to: "Lil Jesus", Cattle Prod, Club, Combat Knife, Crowbar, Gold Nugget, Knife, Louisville Slugger, Refined Uranium Ore, Ripper, Rock, Sharpened Pole, Shiv, Sledgehammer, Spear, Super Sledge, Switchblade, Uranium Ore, Wakizashi Blade, Wrench
Melee weapons is a combat skill, meaning it affects your chance to hit, critical chance, and damage with the respective weapons. The only confusion that could occur would be that non-ranged weapons that use energy cells (ex: Cattle Prod) are no considered melee weapons, and brass knuckles and power fists are considered unarmed. Melee weapons can be very powerful, as well as a great change of pace or someone who has already played a sniper character. It can also work as a backup if enemies wander too close. Before choosing to tag this skill, consider unarmed as well, both remain viable throughout the game.

Base Formula: 5% + (EN + IN)/2
This skill effects your chances of getting special encounters on the map, weather or not you'll get the option to enter an encounter, and where you are when you do enter an encounter. In general, I would recommend that players not tag this skill, as it's use is far too narrow. Also of note is the fact that scout guides scattered through the game can raise this skill when used, but not above 91%. If you have a motion sensor in your inventory while traversing the world map, it will give an effective +20% to your outdoorsman skill.

Base Formula: 20% + IN
Repair is used to fix things, but a lot more as well. The repair skill can be used to disable robots, heal friendly robot NPCs, deactivate forcefields, and complete several quests. Your effective repair skill can be increased by 20% by placing a tool (actual item name, not just any old tool) in your active item slot, and 40% by placing a super tool kit there. Neither items are used up over time. Repair can be increased by reading dean's electronics manuals that are scattered throughout the game. Tagging repair can be a bit of a gamble as it's rarely usful, but when it is it tends to help a lot.

Base Formula: 25% + (2 x IN)
Science is needed to understand computers, medical technology, and a handful of quests. It is used both passively to determine dialogue options and observations, and actively on computer terminals and other objects. This skill can be increased up to 91% by reading big books of science that are found rarely in the game (they are less common than other books). The only reason I would tag science is to get the best brainbot later in the game, which requires at least 121% science skill.

Small Guns
Base Formula: 35% + AG
Applies to: .233 Pistol, .44 Magnum Revolver, 10mm Pistol, 10mm SMG, 14mm Pistol, 9mm Mauser, Assault Rifle, Combat Shotgun, Desert Eagle .44, FN FAL, FN FAL HPFA, H&K CAWS, H&K G11, H&K G11E, HKP90c, Hunting Rifle, Johnny's BB Gun, M3A1 "Grease Gun", M72 Gauss Rifle, Needler Pistol, Pancor Jackhammer, Pipe Rifle, PPK12 Gauss Pistol, Red Ryder BB Gun, Sawed-off Shotgun, Shotgun, Sniper Rifle, Tommy Gun, XL70E3
Small guns is a combat skill, meaning it affects your chance to hit, critical chance, and damage with the respective weapons. If the list above doesn't make it clear enough, small guns covers the largest batch of weaponry in the game. If you tag small guns, it can easily take you through to the end of the game as long as you continue to move up to the best weapon you find (which will be fairly often).

Base Formula: 25% + AG
Sneaking can be fun if at a decent level, and frustrating at a lower level. When sneaking all npcs around you must roll against your skill, and have their perception halved if they fail (meaning they didn't notice you). with a high enough sneak skill, one can kill npcs without other npcs taking notice, which becomes very important later on. Sneak is a toggled skill, meaning that you must turn it on for it to work. This can be done by using the skilldex button, or simply pressing "1". Without the silent running perk, running (double clicking) will cancel sneak. If you plan on playing a stealthy assassin type character, sneak would be a good skill to tag as it continues improving well past 100%.

Base Formula: 25% + (2 x CH)
Speech allows your character to get away with lying, argue their points well, and talk their way out of jams. With a high enough speech skill it is possible to make it through the game without having to enter combat with another human, though it does get difficult at times. Speech skill above 100% has very little additional effect, so I would not recommend tagging it unless you're attempting a speed run of the game, or simply want to play a diplomatic character.

Base Formula: 20% + AG
Stealing covers taking items from NPCs, taking items stealthily from containers, and planting items on NPCs. Aside from getting spare ammo and cash off of towns folk, steal has some less obvious uses, such as planting timed explosive in people's pockets. It is important to note that steal is effected by facing modifiers (it's best to stand behind the target) and size modifiers (it's easier to steal a coin than, oh, say a piano or flamethrower) in addition to a skill check. There is a bug associated with steal and some containers, desks and workbenches, that will allow you to take items from them with steal even if they are locked. Unless you're planning on building a completely stealthy character (and even then) I would hesitate to tag steal, simply because a failure can turn an entire town hostile.

Base Formula: 40% + AG
Applies to: Flare, Gold Nugget, Grenade (Frag), Grenade (Plasma), Grenade (Pulse), Molotov Cocktail, Plant Spike, Refined Uranium Ore, Rock, Sharpened Pole, Spear, Throwing Knife, Uranium Ore
Most thrown weapons double as melee weapons, such as spears and knives. When throwing, your strength statistic determines the maximum range, not the skill. Grenades are one of the few reasons to put any points into this skill, unless you want to play a thrower as a challenge. Other than grenades, rocks, spears, and knives can be thrown. As a warning, if your skill is low, that grenade might land at your feet rather than at your target. Due to it's limited use, I would not recommend tagging throwing.

Base Formula: 20% + (PE + AG)/2
This skill is used for both setting and disarming traps and explosives. Without at least some skill in traps, you won't be able to see them before they go off. The message to look for is "You see a raised plate", or the status window will inform you that you've spotted a trap on the door or container you tried to open. With poor traps skill an attempt to disarm a trap might set it off, and an attempt to plant a timed explosive might get you blown up. I would not recommend tagging traps simply because explosives and traps are simply too rare in the game, though it is fun to arm explosives and plant them on a person via the steal skill.

Base Formula: 65% + (AG + ST)/2
Applies to: Boxing Gloves, Brass Knuckles, Plated Boxing Gloves, Power Fist, Spiked Knuckles, and empty item slot
Unarmed is a combat skill, meaning it affects your chance to hit, critical chance, and damage with the respective weapons (or lack thereof?). Unarmed can be attractive as it requires no ammo (unless using a power fist) and can deal considerable damage. The major concern is getting close enough to hit an enemy without getting shredded with bullets, a concern which sneak remedies well enough. Unless unarmed is the core of your character, or a backup to a ranged combat skill, I wouldn't recommend tagging it. It is notable though that there are several perks that make unarmed one of the best damage-dealers in the game, but the entire character must be dedicated to it. As you gain in levels, your empty-slot attacks will change:
Punch (Mode #1 - 3 AP)EffectRequirements
Strong Punch+3 DamageUnarmed 55%, AG 6
Hammer Punch+5 Damage, +5% CriticalUnarmed 75%, AG 6, ST 5, Character Level 6
Haymaker+7 Damage, +15 CriticalUnarmed 100%, AG 7, ST 5, Character Level 9
Punch (Mode #2 - 6 AP)
Jab+7 Damage, +5% CriticalUnarmed 75% , AG 7, ST 5, Character Level 5
Palm Strike+7 Damage, +20% Critical, Pierces ArmorUnarmed 115%, AG 7, ST 5, Character Level 12
Piercing Strike+10 Damage, +40% Critical, Pierces ArmorUnarmed 130%, AG 7, ST 5, Character Level 16
Kick (Mode #1 - 4 AP)
Strong Kick+5 DamageUnarmed 40%, AG 6
Snap Kick+7 DamageUnarmed 60%, AG 6, Character Level 6
Power Kick+9 Damage, +5% CriticalUnarmed 80%, AG 6, ST 6, Character Level 9
Kick (Mode #2 - 7 AP)
Hip Kick+7 DamageUnarmed 60%, AG 7, ST 6, Character Level 6
Hook Kick+9 Damage, +10% Critical, Pierces ArmorUnarmed 100%, AG 7, ST 6, Character Level 12
Piercing Kick (9 AP)+12 Damage, +50% Critical, Pierces ArmorUnarmed 125%, AG 8, ST 6, Character Level 15