In the early "oughts", I had a pretty large and varied group of players. I was running weekly Dream Park one-offs (really, anything from moldy James Bond 007 scenarios to expanded cross-genre ideas found in magazines) more or less with a first come first serve policy, so though I had a dozen players or so, they alternated spots - perfect for our tight schedules.
At one point, I wrote a guide that treated them as "problem players" and how to handle them. Not that they truly were, you understand, but a GameMaster has to deal with his players' quirks. Here is that long-lost guide (names changed to protect the moronic):
Gloves gets easily frustrated or impulsive if answers don't come up right away. My solution: Let him sulk and concentrate on the other players. ;-)
Absolut WILL sacrifice himself if need be, which could lead to unwanted character death. My solution: Fudge rolls to save him at least some of the time, but have him suffer mentally at every turn.
Twelve gets dangerously violent, but is really good at thinking outside the box. My solution: Keep him away from good weapons and throw more "impossible" situations his way (while Gloves sulks, I guess).
Willow wants to role-play more, but always winds up taking the combat solution. My solution: It's what he actually really wants, so make sure he has combat to keep him happy.
Gahkar tends to kill helpful NPCs and betray the party, but he's really good. My solution: Make his character's life miserable, and only really take him out toward the end.
Sherlock is skittish about even coming in to play and leaving his girlfriend at home, but he really enjoys himself. My solution: More games that specifically attract him, at least when I advertise them.
Psycho is a crazy madcap loon, but oh, so entertaining. You just never know what he's gonna do to derail the whole thing. My solution: Take it like a man.
Red goes for the jugular every time, never side-tracking even for interesting bits. My solution: Giving him something time-consuming to do plotwise, while the others linger to taste the flavoring.
Dash likes to come up with fun, but not useful, concepts for characters. My solution: Let the bad guys ignore him most of the time so he's relatively safe, and give him latitude in what he can do with his silly abilities.
Willy always plays his characters as silly caricatures and will always do the stupidest things no matter his character's IQ. My solution: Laugh, then sometimes just call it a joke that was "never said" or "never actually happened".
J basically does nothing, says nothing even when addressed, and contributes very poorly to any adventure, but he's a nice guy. My solution: Make him the center of attention, in the same sense that the calmest part of a hurricane is its eye. Whatever that means ;-). Being at the center doesn't mean he does more or HAS to do more. It just means the story's occasionally about his character. Result: He feels like he's an important part of the story, when his actions really aren't (by his own choice).
Well, that's a cross-section of my group, and what I did with them in those halcyon days... How do YOU deal with your players' particularities?