Best inexpensive science toys and games [View all]

[unrepentant progress]

It's that time of the year, so I thought I'd ask DUers what their favorite inexpensive science toys and games are to give friends and families.

For the past couple of years I've been giving copies of Kerbal Space Program. It's a 100% non-violent game where kids of all ages can design and build spacecraft Lego-style, then use them to explore an entire solar system. It's also realistic enough where you can actually use it to learn pretty advanced physics and astrodynamics. I keep telling people you don't need to learn rocket science to enjoy the game, but if you do it only adds to the fun. And if you get bored with the stock game, there are all kinds of community created projects to modify and extend it.

So what are your favorites?