Pacman clone with 2 pacmen:
http://home.tiscalinet.de/xception/java/2PAC.html
http://fubz.us/games/bin/screenshot/2pac,man!.gif
Control both pacmen with arrow key.
Making use of the second PacMac works better than i expected. How about adding multiplayer to it (using one computer/keyboard of course, not networked). I can imagine that it would become a nice game for smaller children, because you’ll get the feeling of playing together without the need to work together. You could add a mode with separate scores for each player and one with a shared score…just remove the cigarette item from the game for that… ;D
You need some visual indicator of when the power pill is about to wear off.