What Is It? game 251

W00t! It's time for another collaboration with the always-excellent What Is It? Blog. Can you guess what this strange object is used for?

Place your guess in the comment section. One guess per comment, though you can enter as many guesses as you'd like. Please do not post any web link or URL - doing so will void your entry. You have until the answer is revealed on the What Is It? Blog tomorrow.

Two prizes: the first correct guess and the funniest yet wrong one will win a T-Shirt from the NeatoShop.

IMPORTANT: Please write your prize selection alongside your guess, so visit the NeatoShop and take a look around. If you don't write your prize selection, then you don't get the prize. I think you'll like the selection of funny t-shirts and science t-shirts -or even t-shirts of your favorite blogs and websites.

For more mystery items, go to What Is It? Blog. Good luck!

Update: the mystery item is experimental XM75 40mm grenade launcher, probably made by S.A. in the late 1960s. The first person to guess grenade launcher was Berhard, who wins a t-shirt from the NeatoShop! The funniest answer of the week came from Colshorts, who said these were $250,000 Military Pencil Sharpeners. That's also good for a t-shirt! Find the answers to all the mystery items of the week at the What Is It? blog.