Mage, fighter, assassin, thief, blade, pit dog, order member, knight (three types), merc, deadric lord?
I read an interesting story where a member of the dark brotherhood catches the player doing quests for the thieves guild, and bitches them out for being dressed as the archmage.
"About that..." replies the character.
Because you could lead all the guilds.
I actually found that fairly liberating. I gave up on Deus Ex: Invisible War because the game kept bitching me out for not specializing.
In NV I've been sneaking around with silenced weapons killing legion members while being dressed as a legion recruit, and it feels seriously OP.