Saboteur card game [rules are easy enough to learn] - its great for groups of 4 - 10 ppl to play!
Much cheaper than the $25 AUD price I've seen in stores.
[If you buy more than 3 it becomes slightly cheaper than USD$7.70]
Do note it's Deal Extreme so :
1 - you need extreme patience to wait for their shipping (notoriously slow in my experience).
2 - Expect the quality to be commensurate with the price.