The Game A Day Project: Fluxx by Nathan P.
"Fluxx is a great mellow game. If you're not familiar, you start with a basic rule (draw 1 card, play 1 card), and you can play new rules (from drawing and playing more cards, to randomly playing cards, to getting bonus's for certain game conditions, and so forth) in addition to goals and the cards you need to fulfill the current goal and win the game. .... It's totally still not a serious strategy game, but it does give an element of player-vs-player challenge that I find engaging."