Rummy, plain ol' Uno, chess, and Duck Duck Goose.
Since I work in childcare, I often get the opportunity to participate in playground games--Red Light Green Light, What Time is it Mister Fox?, Red Rover, various forms of tag, Hide and Seek, and Simon Says. We tried to play Duck Duck Goose a couple weeks ago, but some of the younger kids didn't quite get the gist of the game. It didn't last more than 2 rounds.
