Over the summer I stumbled upon this post about playing war with logarithms. The idea is simple. Evaluate the log, the person with the biggest card wins. In the event of a tie, there is a 1-card tiebreak. I didn't observe stacking tiebreaks, although I'm sure it's possible. Prior to playing the game, we talked about logarithms as the inverse of exponents and how 3^x = 9 equates to log_3 (9) with the answer to both being 2. Anyway, rumor is that kids love this game so I was optimistic. I took the cards that Kate Nowak links to and modified them a little bit to make a better distribution of numbers (most of the cards in their sets evaluate to 2). I finished with a set of 40 logs, printed them on mailing labels and had my student teacher affix them to index cards that had been cut in half. I gave each color group their appropriate color deck of cards. We had a brief demo and then I let them loose.
I'm not sure how to describe it properly, but watching the results were A-MAZING.
Now, I had a couple boo-boos on the cards but that didn't turn out to be a big deal. Doing spot checks it seems they were evaluating them properly and letting the correct person win. I told them the game was over when one person was totally out of cards. Every group played a couple games without getting bored. The only consistent thing I noticed is they were counting the zeroes when comparing log 1000000 (6) and log 10000000 (7). A few times I noticed they would think it was a tie until I pointed it out.
More interesting in action (and a nice way to test YouTube auto-blur, which seems to think hands are faces at times):
If you're interested in the set I used (boo-boos and all), poke around my Algebra II resources.