Phantasy Star Online for insanely long and chill co-op play sessions. Your friends could bring their own solo characters over with a gamecube memory card and load into your game as you embark on an action RPG hack and slash adventure with real time combat. Add in bosses, quests, rare item collecting, and PVP mode and you were in for a fun night!
RE: 24 HOUR CONTEST! Best Co-op Video Game?