Feats, Traits, Edges, Merits, Flaws, Powers, Weaknesses, Strengths ... Different games have different names, but most games have some iteration of these descriptive characteristics that have mechanical effects (i.e. have a tangible influence on die rolls or whatever device is used for determining your ability to succeed or fail at a task). Some games will limit you to just one or two, some will flood you with so many choices you could never possibly use them all. For some games, it's the only mechanics you get.
The value of, we'll call them 'descriptive traits' in a general sense, is that they allow you to both define the character with something that has more than just roleplaying value. Don't get me wrong, for some games and some groups, the roleplaying element is of greater value. While I can recount almost all of the exploits of my characters from games in the last six years, the most fun I've had has been doing things that a) had nothing to do with the plot; and, b) had little to do with the clearly defined skill numbers listed on my character sheet.
Want an example? Of course you do! Picture a small party of barbarians, one of whom was played by yours truly, entering a sophisticated border town, with walls and everything. Now, nothing in my skills said that I needed to subvert the local gang culture, attempt a coup vs. the governor, and then when that failed, burn the city and make off with a herd of cows. But Traefon [character] did have a descriptive trait labeling him as a 'opportunist', and when we thwarted a local gang's attempt to mug us, it was just too good an opportunity to pass up. I was very rarely able to use the exact benefit granted by that ability (it had something to do with tokens), but I didn't let that stop me from role-playing a character who jumped at every opportunity for gain, letting circumstance guide him to new heights.
And cattle wrangling.
Granted, that character's life was cut dramatically short when he saw an opportunity to save a teammate (quite heroically, thank you very much, and totally unappreciated) and ended up impaled on a lizard-person's spear. I should've made my next character a hunter with "lizard-person" as his favored enemy, in memoriam. Too little, too late.
Yes, I'm vindictive, even in another life.
Spycraft 2.0 is one example of Feats Gone Wild! I was advising a player on level advancement based on some of the class skills and feats he would gain for different options, and made a comment that anyone who could memorize the effect of every class ability and power in Spycraft would deserve a medal. And probably psychiatric treatment. Spycraft feat selection is so complex, they have (working off memory here) 10 different feat categories, each with at least 10-15 feats. If you work your multiclassing right, you can easily pick up 16-18 feats by level 20.
Iron Heroes is another example, but unlike Spycraft, the opportunities for picking feats is much more limited. Iron Heroes creates long Feat Mastery chains that allow your character, whose fighting style is already very limited by your class choice, to specialize even more by choosing a particular feat chain. Whereas in Spycraft you could be an awesome mixed martial artist, able to fight using a dozen different styles (wrestling, boxing, brawling, etc.), in Iron Heroes you'll be the girl who can do one thing so marvelously well it works every time ... except when it doesn't. The worst thing in the world is to be an Iron Heroes Executioner fighting someone with sneak attack immunity. It gives new meaning to the word "impotence".
Not necessary an important meaning, but new meaning, still.
But what about Flaws? Sorry, this blog post has gone on long enough. I'll save that for another day.