I would have to say the best one I can come up with is Donald S. Cherry and his dog Blue from Rockem Sockem Hockey videos.
Tom and Jerry! Sure Tom always tried to eat Jerry, but there were a lot of instances they acted like friends.
@ RttaM You won a code!!! Sent it to you. Lot more codes to be won. Keep the entries coming! In the meantime, Check out this scene from the game. Cool, ain't it!