Old amp

Build an isolation box with a mic clip inside. Use it to record with the volume cranked while preventing any unwanted complaints from the neighbors.

If you can find a cheap mid-range horn driver, you could build a talk box.

http://www.generalguitargadgets.com

Take a look at the guitar effects - Filters - Talk-box

I recently ordered a mid-range driver from MCM Electronics and plan on use my old amp as the talk box amp. I'm currently building my own A/B box (but you could buy one pretty cheap).

If you have any experience with electronics it will probably be a VERY easy project. The site says that the hardest part of the project is connecting the plastic tube to the driver.

Thanks for those two great ideas guys! There goes my chance for a lunchbox/time machine combo though...