Broken sword, well one of your main characters, the chick, has a french accent. I guess the guy is american....
Sombra Negra mentioned Republic commando, I believe the accent is new zealand, as I think they hired the same actor to do the voices as who played boba fett, and hence all the clones, in star wars ep 1-3.
In saints row 2 you have the option to give your character a thick cockney accent.
Elder scrolls oblivion has lizard man and cat people accents, but main character is silent.
People are mentioning a lot of games where the main character doesn't actually talk, is Far Cry 2 like this? Lots of great south african accents there! Someone mentioned Nico Bellic being italian, they need to play the godfather 2!!