Bulk Silly Putty
A co-worker regaled us the other day with stories of 50-pound boxes of Silly Putty, available by mail-order. (Apparently a 10-pound ball, thrown with the right force against a hard floor, can bounce up and smash a hole in the ceiling.) I just stopped by the Silly Putty website to look for it; they don't appear to be selling any 50-pound boxes, but they do have 5-pound blobs, for $50, in a variety of remarkable colors, in the Silly Putty Store (in the bulk section).
You can also read about Silly Putty history. "1945: Determined to find a use for the bouncing putty, General Electric sends samples to engineers worldwide. No practical use is discovered."