Tempest - Live Wire
Two screen, simultaneously two player Tempest where you're shooting at each other from opposite sides of a playfield with enemies coming up from the middle and attacking both sides.
Packy-kong
Donkey Kong except with Pacman characters and you have to eat all the dots too instead of just making it the top
Spy Hunter II - Spy Harder
What thw Spy Hunter sequel SHOULD have been, which is a simutanous two player game that is top-down and has the same style graphics and game play as the original, but with more enemies and weapons.