Instructables user rabidiga made this pan flute. It was his entry in a contest to build a post-apocalyptic musical instrument for under $30. He didn't spent a penny, but only used materials that he already owned:
Super easy to make. Took me about an hour even though I am clumsy as hell when it comes to working with wire. Depending on your choice of supplies it could have easily been finished in half the time. And while they don't sound perfect I was able to belt out a killer 'Ode to Joy' even if it was a bit out of tune.
Link via Everyday, No Days Off | Previously: Tampon Pan Flute
@ Ted -you can purchase empty shell casings. Depending on caliber, if they are rimfire or unspent, prices differ. But he recommended getting them for free from a shooting range.
I once made a hand bag/clutch purse from casings. The casings looked sort of like bamboo. It was spectacular.