Gamma 4's game design challenge this year was to make a game where you only use a single button on the Xbox 360's controller (though they could be computer games that used this premise). Which sounds like a restriction that could either work brilliantly or not so.
Among the games designed for it, we have No Fun Games' Pax Britannica, a one-button RTS. Available for Windows at the moment (with a later Mac and Linux version reported), the game sets you up as a factory ship. The one button is used to launch other, smaller ships to attack your foe/s. Hold it long enough for a teensy, fast flying fighter; the mid-sized but deadly bomber; or the fairly substantial frigate, who launches heat-seeking missiles. The last bit is an upgrade to allow for your resource to grow faster.
The game supports up to four players (either through four controllers, or through the keyboard by pressing A, F, H, and L respectively) and is downloadable here in the TIGSource forums.
Just because it is one button does not make the game easier, however. Trying out my one-button pressing skills against the computer AI, I managed to lose two of five games. The strategy I managed to use most often was to create a buffer zone whereby I could go for the resource upgrade, and learning to counter what ships the enemy had out.
Playing against the AI was a five-minute or less chunk out of my day spent per session. I can only imagine the amusement with more players.