For those with a shorter attention span, there's an addictive card game in which changing the rules is a move: http://www.wunderland.com/LooneyLabs/Fluxx/
If you get a play 3 or play all out in the first turn, and someone else has 2 keepers that match a goal card, someone can then win by playing all three.
I'm a fan of the zombie version, which is a hoot.
I felt it failed to live up to the promise of its concept.