Sumouse is a two-player fight-a-thon which may result in your computer being mouse-less. Both players control a small box on the screen via a single mouse.

Each player holds down a mouse button, then frantically attempts to move the box into one of the outer boxes of their respective colour. Your score decreases if it moves into your box, and the first player to reach zero wins. However, if you let go of your mouse button, your score will begin to shoot up again.

Simple, destructive fun - you might want to plug in an old mouse, though. Grab it from here.