Movie night. Everyone has movies they want to watch but how do you decide which one? I built a spinning prize wheel to help randomly choose what movie we watch each week. Of course it'll be useful for other things too. Piece of plywood spinning on a bearing. Spins really well, almost too well. It goes for a while. Flapper/arrow is made from a thin piece of project board. (1/32 inches, I think.) It's very flexible and will probably break, at which point I'll likely replace it with an old credit card or something.
This wheel is made of plywood and seems to be weighted and biased. We don't use it anymore, but it's still probably random enough for most situations.