Self-explanatory. Personally, I'd have to say Navi from Ocarina of Time. Yes, hearing her say "Hey! Listen!" every so often could get really irritating, but she gave you info on what you were fighting, which was helpful and made me feel like I understood the game's world better. It just felt like her heart was in the right place.
So, how 'bout you guys?
So, how 'bout you guys?