What are some ideas for improvised musical instruments?

So last night one of my old musical projects was re-invented and brought back from the grave as a lo-fi/electropop/garage rock outfit when my good friend and I got together and started writing music.

We use a lot of weird instrumentation as of now: toy accordions, kazoos, shakers made out of water bottles filled with beads, etc. We want to stick with this kind of instrumentation and I’m interested in experimenting with home-made musical instruments. I’ve already built a cigar-box banjo and a few shakers, but I’m interested in things I can do that are a little more out of the box, so to speak.

What do you suggest, Fluther?