A while back I got a LOM Geofon, which is a contact mic with a few attachments. It came as a kit and I got it assembled (really, just soldering a few connections) and it was fun to use. Except for the stiff, noisy cable.
I replaced it with Mogami 2552, and I get less handling noise now. Nice! There might be thinner, limper cable out there, but this stuff was an improvment.