I recently built these two tiny robots from coin cell batteries. I love the coin cell battery holders because they let me solder a permanent connection to the pager motor. My red-eyed bot actually has a switch, which I salvaged from some old electronics. Some helping hands and a magnifying glass made the soldering fairly simple. This robot was made possible after viewing How to Make a Mini Bug Robot.
Lenny, shown below, is made from electronic components I salvaged from a variety of e-waste items. His body is built from a printed circuit board taken from the inside of a kid’s calculator. While Lenny lacks a switch, he makes up for it in character.