Tetriminos

I love these lights. They belong to Scoobyben, and you can stack them any way you like; as long as they're all touching each other (in an awkwardly precise fashion), they light up. They're horribly impractical, a pain to turn on and off, and fall over if you jump too heavily nearby, but they're really, really cool.

I also find this photo pretty cool. It makes me happy.