Wacko is a 1983 arcade game by Bally Midway. This title takes the prize for having the strangest dedicated cabinet ever made (a fact that has thankfully kept most copies of this rare game from being converted to other titles).
The Wacko cabinet is sloped, both the control panel, and the marquee are set at an angle. The right side of each being about three inches lower than the left side. This means that the joystick and trackball are both at an angle. (The trackballs actually had to be modified at the factory to work properly on a slope). This is the only machine ever made to feature a sloped control panel (a distinction which it will probably keep for a long time).
The game itself is a colorful single screen shooter, with excellent graphics for the time. You maneuver "Kapt'n Krooz'r" ( a green alien, whom Midway was hoping to make into an icon like Pac-Man) around the screen in his spaceship. The terrain is an orange moon scene, various cartoonish monsters dot the landscape. You must blast the monsters in pairs to make them vanish (if you shoot 2 wolf monsters in a row, then they will both vanish, otherwise they remain). Later levels introduce even more complex rules as to what can be shot.
You control your ship with the trackball, while using the joystick (with top mounted fire button), to aim and shoot. The controls feel natural with a little practice, but the game quickly becomes very difficult on the higher levels.
This is a rather rare and valuable game, your best bet for playing it is the MAME emulator (set up your controls like they would be when playing Quake for best results).