Since I started posting about how to make characters unique, I thought I should address one of the most common systems added to the game for that purpose. I'm aware that this topic has been covered pretty thoroughly and that I'm probably not offering much of anything in the way of fresh insights, but I felt like stating my reasoning in my own words, so here it is.
My introduction to skills came via the Gazetteer series of supplements to the Known World/Mystara setting introduced in the Expert Rules set, specifically GAZ6, The Dwarves of Rockhome, which happened to be the first one I acquired. Briefly, every character got four skill slots plus his Intelligence bonus, with additional slots gained at higher levels. Each skill was based on an ability score, and checked by rolling d20 against that score. The list of skills, accumulated over the entire run of the Gazetteer and Creature Crucible series, included things such as crafts (blacksmith, cobbler, armorer, weaver, etc.,) knowledge of whatever field you choose, acrobatics, dancing, singing, musical instruments, labor and professional skills (mining, engineering, sailing, cooking, etc.,) gambling, art, law and justice, alertness, weather sense, direction sense, healing, bargaining, persuasion, riding, tracking...the list goes on and on. Some skills, such as quick draw, fighting instinct, and blind fighting even granted combat bonuses.
The system appealed to me immediately for its promise in making characters more than just generic members of a class. At a glance, skills seem to do just that, defining a character's
training and interests not directly related to the functions of his
class, and since my players at the time were fairly experienced and game-savvy, they didn't have much trouble adding skill selection to the character creation process. Until pretty recently, in fact, I thought of a skill system as an essential part of my game. A few things have led me to rethink that view. My new group, with only one veteran player, found the skills confusing, and fretted about choosing the ones most useful in an adventuring career. Skills did not serve to add depth to their characters, but to gain bonuses and define what they could and could not do. And of course, I had begun to read the ruminations of some old school game bloggers that clearly articulated a lot of my vague misgivings about the skill system and added even more that had never occurred to me. In particular, -C of Hack and Slash has done a fantastic job of deconstructing skill systems and individual skills.
Using my own recently articulated framework for analyzing complexity, realism, and choices, here are my conclusions on skills.
Skills certainly do offer up a lot of additional options, but the placement of those choices and their actual interest are dubious. Skill systems heavily front-load choices into the character creation phase. Most of the choice comes in the form of whether to take the skill in the first place, very little in whether and when to use it in play.
I divide skills into two admittedly nebulous categories: Those that are directly and commonly useful in adventuring, and those that are mainly for role playing color and flavor. The first sort are prone to either limiting the scope of choice in play, or else contributing to bonus inflation. To be worthwhile at all, having a skill must provide an advantage over not having it. That necessarily means that either characters who lack the skill are penalized or barred from attempting actions relating to it, or else characters with the skill get a boost over and above the baseline of ability assumed in the game. It's debatable whether the "useful" skills actually expand the range of
choice during an adventure at all. At best they affect the odds of success of a
particular action, but they generally don't open up completely new possibilities. You can attempt to persuade someone without having the persuasion skill; you can bargain without bargaining skill; lack of mining skill doesn't prevent you from examining a cave wall or trying to tunnel through the wall with a pick; you can run and jump without athletics skill.
The choices implied by the "color and flavor" skills, the cooking and crafting and singing and all that, are generally ones that players wouldn't try without them, but also aren't all that interesting to most players. 99 times out of 100, a painting or leather-working skill roll has no significant consequences in the game.
Skills add only a little complexity to actual play, but a lot to character creation. The relatively uninteresting range of choices they add to game play doesn't even come close to offsetting this unless your players really know their way around the D&D game. Even then, it's iffy. It may be moderately interesting to make your character a singer or a blacksmith, but it has precious little application in play beyond a role playing hook, and that can be accomplished without codifying it into game mechanics.
Having failed the interesting choices vs. added complexity test, assessing realism is more or less a moot point, but the skills system does produce some wildly counter-realistic results. For one, it allows a character with a high requisite ability score to be an instant virtuoso, while one with an average score can never be more than mediocre. Worse, a character with a high score in a particular ability can load up on skills based on that ability, and be a virtuoso in multiple fields. A character with a 17 Intelligence can begin play as a master blacksmith, tracker, shipwright, and alchemist, trades that each should require years, if not decades of diligent practice to attain mastery. It's terribly unrealistic for someone who deserts the family farm at the age of 16 for a life of adventure to be a better farmer than his father who's been toiling in the fields for a quarter century simply because he has a higher Intelligence score.
In my opinion, the skill system fails at what ought to be its primary purposes. It doesn't add much in the way of new options in actual play - in fact, it subtracts from them. As a means of distinguishing and individualizing characters, it's a Rube Goldberg device, and it even fails the lowest priority, the realism test. Its cons far outweigh its pros in my estimation, which is why it's no longer a part of my game.