Your pretty sure... HUH...Hey everyone Hellbinder is pretty sure. I know for fact Duke , Blood , most build games had co-op I played all those games on TEN . Never played Nolf. Did DOOM have co-op, dude are you for real. Never played Quake 1 but I know for a fact Q2 had it and it was released in 98, unreal had it too. Games like Deus EX, Thief , Jedi Knight ,ect didnt have it. I'm not sure if Half-Life had it but I thought I palyed co-op with buds threw that game.