I know you said co-operative, but Knights was always my favourite 2 player game (It may have had a co-operative mode).. Top view maze game with various objectives, and tons of great gameplay... trapped chests, zombies, bats, spells, shovels, axes, what more could you ask for? =)
Better than Carnage if you ask me, and one of the best AMOS games I ever played (you'd never know except for the LeftAmiga-A thing)
Knights242.lha game/2play 223K 466 Two-player violent dungeon bashing