First off, I feel compelled to tell you that these are less dirty than they sound. Honest.
That said, have you heard of Bucky Balls? I hadn’t, but they’re apparently little earth magnets—super strong—that can be used to create all kinds of creations.
Amazon has that set for $30 with a $5 credit at checkout, so quite a bit cheaper than they are elsewhere. Very cool, but not for kids under 12 or households with small creatures who might try to eat some delicious earth magnet snacks.
(And a bonus: I found those by accident while I was looking at Qwirkle, which is down to $20 and is a 5-star, award-winning smartypants game I’ve been stalking. )