I heard they re-used voice assets for "Black Bolt" that were recorded for a now-defunct Fantastic Four video game for Gordon Freeman.... pay close attention and they sound exactly alike... I mean Gordon is exactly like I'd expect Black Bolt to sound from reading comics and everything... I can't believe nobody heard about this or noticed the coincidence before now....IFS said:Gordon Freeman is fully voiced in half life 3
Others have pointed out Saints Row, which is probably my favorite example considering they not only became voice acted but got a choice of a number of different voices (exact number depending on the game).
For a non-game character Longshot from Avatar the Last Airbender only speaks in one episode long after his introduction if I remember right.