Pika-Boo! on 22 October 2008
Hrmm a tough one...
Well for me it would have to be a toss up between...
Goldeneye and Perfect Dark's multiplayer modes on N64 - me and my little bro used to kill hours on end on those.
Although the original Mario-Kart on SNES (Yes I am really that old!) would give them both a run for their money (again multi-player).
