Here's a nice o­ne from Scythe. The "FOLDABLE MOUSE" reminds me of something that should have come out in the 80s, but I guess some inventions just take their time. As indicated, the mouse does indeed "fold."

Scythe introduced the "FOLDABLE MOUSE (FW-WH/BK)." Two body colors are available: white and black, where the actual retail price is 1,480 yen.

Though there are a number of mice that have some consideration for portability thanks to..just being smaller of offering a place to store the cable, this "foldable mouse" is unique in its case construction. The back portion of the mouse o­n which the palm rests is actually hollow, and when this is slid the front portion of the mouse can be stored inside it -- this drastically reduces the length of the mouse. When stored, the mouse is a mere 63mm long. The cable itself cannot be stored, but since a reel mechanism is offered, it doesn't seem to be that annoying.

Main specifications include a size of 57 x 25 x 149mm (W x D x H, when open), an 800dpi resolution, 3 buttons (L/R button, wheel button), and a 70cm cable. A pouch is also included.

You'll be able to say that this mouse is oriented towards use as a carrying mouse or mouse that you use o­nly o­n rarely used servers.

Inspired by (with more pictures of the folding action):
http://www.watch.impress.co.jp/akiba/hotline/20050618/etc_foldmouse.html

Product Page:
http://www.scythe.co.jp/input-device/20050615-190809.html