6-man team. Support, sharpshooter, medic, commando, demo, and berserker.
That's my dream setup. You've pretty much got all bases covered; support, commando and berserker for crowd control, medic for healing, and sharpshooter and demo for big stuff (and support can aid them should the need arise). You might be wondering why I left out Firebug. It's not because I have anything against the firebug, it's just because I think other classes fit the role of crowd control better (firebug is more of a force multiplier; weaken the crowd so the other guys can clean house more easily). I always seem to have the most fun when I get a match with a team like this (although firebug can substitute commando and I won't have a problem).