Skills determine the mastery of a given field, by a character, e.g. bartering or machine guns. Unlike attributes, this knowledge can be increased with each next experience level. Skills have been divided into three categories General, Weapon and Knowledge. A skill can be passive or may need to be activated manually. Weapons are passive skills (weapon handling), knowledge - activated (e.g. cracking a safe). The general ones refer to both types.
Animal Whisperer - the ability to tame wild (and not only) beasts. Such animals won't attack and in some cases can even join the team and fight by your side. Despite we can't really talk about a huge amount of damage dealt by the animals, they can serve as a good distraction for your enemies. Moreover, after taming a beast, the team member that did it will gain additional points in the skill that is connected to the animal (for example +1 Charisma for taming a dog). This ability is not particularly useful, but it sometimes can be of help during some quests, like calming down terrified cattle or bringing back a lost dog.
Barter - each point decreases prices on goods by 1%. It is a value that is shared by the entire party. At the very beginning, it may be useful, because you will, most probably, suffer from ammo shortages, but in fact it is not that important to be maxed out. After the game enters a more advanced stage, money will not be a problem anymore.
Brute Force - allows you to ram though blockades and severed walls. It is a useful skill and it is recommended that one character has it, around level 5. However, this does not need to be a member of the initial party. Right after the game starts, you will get an opportunity to include an NPC to your party, who has a high level of this skill.
Smart Ass, Hard Ass, Kiss Ass - three separate skills that work in the same way. You will be able to use them in conversations to obtain additional information from the interlocutor, or discover a new solution to a problem. It is a good idea to reach, at least level 3 in each of these.
Leadership - a character with this skill increases the chances of hitting the target, to the party members. Apart from that, it decreases the possibility that an NPC gets out of control and dos his turn himself. Be initial four rangers are the hard core of the party, who you can always rely on. However, all of the additional ones have their will and may escape when they are wounded, or decide that they want to kill their own way. High Leadership levels prevent that from happening. You can ignore it at the very beginning, but it is a good idea to take interest in that, later on. The range of this skill is set by Charisma, so it is good to develop it in a character that has a lot of points in this attribute.
Outdoorsman - allows you to avoid random fights, while exploring the wastes. And you will be attacked quite often. The upside is that you gain additional experience and loot. The downside - a waste of ammo, first-aid kits and, predominantly, time on negligible "fillers". It suffices that only one of party members has this skill. Level 4 should ensure you with the option to flee almost every random threat, throughout the majority of the game.
Perception - The ability to notice interesting things, like for example hidden passages in locations, or chests with ammunition and shrines, when exploring the map. If some item can be used, it will be highlighted. Thanks to Perception, you will often notice various useful hints connected to the task that you are currently solving. Moreover, it may so happen that you will notice something interesting about the person that you're talking to and you will be able to ask about it. Sometimes, you will discover traps, for example in some safe. One of the team members should have about 4-5 points in this ability, and it will be enough to make the gameplay easier. As you play the game, you should be able to quickly achieve 10 points.
Weaponsmithing - the ability to dismantle weapons to obtain modifications that can be later used in other weapons. To use a modification, you need to have the Weaponsmithing ability, so it is good to develop it in more then one character (but not on every one, because if someone uses only heavy weapons and explosives, no modifications are necessary). Moreover, even if you don't manage to get a modification out of a weapon, you will obtain Broken weapon parts, which you can sell for some good money in the Ranger Citadel, so you don't loose anything. As long as you are in Arizon, dismantle almost every weapon that you know you won't be using.
Assault Rifles - versatile and useful. Deal decent damage with decent penetrability and range. Unfortunately, they use expensive ammo and lots of AP. Apart from that, a character receives a negative bonus to hit, when the opponents is standing too close. They have fire mode selectors in-built, which allows you to save up on ammo or to hit several opponents with one burst, if they are standing in a straight line. This weapon should better not be used by more than two rangers. Ammo being the first reason and there are better alternatives at higher levels, being the other.
Bladed Weapons - weak base damage, but frequent critical hits . Almost useless against armors. More of an alternative weapon, when you run out of ammo.
Blunt Weapons - very high critical damage, even against thick armors. Works excellent as a weapon over short distance, for someone with heavy gear.
Brawling - melee fighting. More of a curiosity, but you can sometimes find an interesting weapon to wear over your firsts. Multiple attacks in one turn.
Energy Weapons - perfect against armored enemies. The damage is scaled depending on the armor, doing little harm to unarmored targets. Moreover, it cannot block nor deal critical hits. Energy Weapons are rather rare and it won't be of much use at the beginning of the game, but in California, when you will be facing huge cannons with armor 8, having a good energy damage dealer is crucial.
Handguns - short distance weapon, for example for a medic. Despite his appearance, such doctor can quickly bring chaos among enemy forces by shooting down single units with one or two shots. They use cheap ammunition and have a low cost of shots. Their biggest disadvantage is low armor penetration. After some time, you will encounter mini-cannons that require .45 ammo and will change your mind about Handguns - they have a decent armor penetration value and very high shooting cost. A medic equipped with such thing, as well as with usual pistol for unarmored targets, will be dangerous to anyone.
Heavy Weapons - the biggest toys, like grenade launchers and heavy machine guns. Very high damage, often AoE. Their disadvantages are: high AP cost and additional vulnerability to melee damage. A character carrying such weapon should have something for close fights in the other hand. It is good to quickly start investing in someone who will be equipped with such weapon, as the battles will depend mostly on them. At the beginning, having enough ammo will be the most difficult thing, because machine guns will use it very fast. The best thing to do, is to prepare a team member with a lot of AP and the Demolitions skill, who will be using Handguns at the beginning and will switch to Heavy Weapons when a solid rifle and a lot of ammunition is available. When using AoE weapons (rocket launchers, grenade launchers), remember to switch to free aim mode (click on the icon of the weapon and select the place that you want to hit, instead of selecting an enemy), to hit as many enemies as you can and at the same time not hurting anyone from your team. Remember not to give any Heavy Weapons to NPCs that join you. You never know when they can oppose your orders and you don't want a rocket landing in the middle of your forces.
Shotguns - short distance weapon. It can hit several enemies at a time, which is useful, but it can sometimes hurt your team members (remember to switch to free aim). This ability should rather be developed in only one team member, as Shotguns are not very practical, especially in later parts of the game. It can serve as alternative weapon for someone with a sniper rifle or a machine gun and also, due to AoE damage, as a quick door opener and a tool for "defusing" mines (shoot at a minefield in the free aim mode to blow up some of the mines).
Sniper Rifles - tremendous damage and long range. In return for high AP and ammo cost, and low damage to nearby targets. A good sniper is capable of eliminating an opponent from afar, in one shot so, there should be a room for one in each party. However, it is important that he has an alternative weapon, which he can use well, e.g. a shotgun. A sniper should be the one to start a fight, due to the long range. Then, the opponents first need to run up to your characters.
Submachine Guns - they use cheap ammo, but they burn it out very fast and deal mediocre damage. Short range and low penetration speak to are also their downsides.
Alarm Disarming - a lot of safes or gates are secured with an alarm (you will know it by nearby sirens). This skill is worth developing if you plan to sometimes depend on stealth tactics, instead of open fights. Even if you don't, Alarm Disarming will still be of use for opening some of the doors in the game. Put some points into this skill, but do not waste them when you have more important abilities to develop.
Computer Science - computer hacking. One of the basic skills, which is worth developing from the very beginning. With that, you can obtain additional information, open computer-controlled locks and repair damaged systems.
Demolitions - the ability to use thrown weapons, such as grenades, and bomb disarming. Grenades are a rarity and you will be saving them up for special occasions. Disarming is useful to, e.g. cross a mine field or disarm a trap. An useful item, but not a priority.
Field Medic - allows you to use healing objects. It should be developed in one character, as quickly as possible. They will then be healing the entire party. In a nutshell - the higher the level of this skill, the better capacity of a first-aid kit to heal and, thanks to which you will save up on them. A character without this skill, can only use weak painkillers.
Pick Lock - another "must have". You open a door, behind which you open lockers with treasures inside.
Mechanical Repair - the skill of fixing various machinery in the wastes. Useful mainly in specific quests, e.g. to fix a well with drinking water. Useful, but you can do well without it.
Safecracking - Opening of safes. The more safes you open, the more valuable items. You only need to watch out for possible bombs in locks (run a Perception check before you start cracking).
Surgeon - healing of injuries in party members and NPCs. Immensely important! The optimal situation is one, in which there are two party members with this skill - one on a high level (at best, the one with Field Medic plus, e.g. two Handguns and nothing more), and the second one with, at least 1-2 points, to perform an operation on the full-time medic, should the need arise.
Toaster Repair - Wasteland 2 developers have of course put something peculiar in the game. Generally speaking, this peculiar thing is... opening some Toasters. You will find them spread around the game world. Sometimes there won't be anything interesting inside, but sometimes you can find some unique items that you will be able to give to the museum in Ranger Citadel or to some NPC, in exchange for a reward (for example weapons or unusual food that increases statistics temporarily). Toasters are not very frequently found, but you shouldn't leave any one unopened, so one of your team members should develop this skill.