Pac Man, Pong and Space Invaders (play free at these links) combined into a complicated but enjoyably productivity-sapping retro mashup. To wit:
To increase your score-bar in Pacapong you simply collect as many pills as possible within the time limit. Once fired your Pacman can be controlled to a small degree, but will always be inclined to heading towards your opponents side. To make things a little trickier (and more awesome) you also have to contend with ghosts, hit them and you’ll lose a chunk of your score bar (unless you pick up a power pill).
To make things yet even more trickier (and indeed more awesome), you also have to contend with Space Invaders who descend your side of the screen whenever your opponent collects them – with some careful manoeuvring you can even shoot them with the pills you collect with Pacman.