One of my favorite multiplayer games on the SNES is Metal Warriors... but it almost never gets talked about as a multiplayer game... and that's a damned tragedy.

The regular game is a side-scroller... kinda medium-paced... difficult:
The gimick that makes it awesome: you pilot these giant mechs and you can get out any time then get into a new mech. It's fun in single player, but multiplayer is ridiculous. You'll be almost dead, but if you can manage to get away/jump out of your mech then hop into a new mech... well, tables turned. We had so many insane moments where one of our mechs was literally on fire... then we'd manage to escape... or sometimes, we'd get out of the mech only to get instantly crushed by another player in their mech. There was much screaming.
If you have friends over, play this.