The buzzer
The other guy that came out of my little building session on that weekend. I wanted to make a solar roller but somehow the motors I had were unable to push even the lightest, most friction-free of my creations. It would work in my hands but as soon as it was put on the ground, the motor would stop. Not enough torque. The geared motors or modified servos I tried were all the same. That, or they just wouldn't get enough juice to even spin while aloft. I was frustrated so I decided to take that little solar engine and plug in a small vibrating motor (from an HexBug). I then got a few lengths of guitar strings, bent and glued them to make legs, hoping they would vibrate and twitch enough to move the little guy around. In the end, as you can see in the video, this robot does not move at all. It does, however, look damn cool (I think) so I allowed him to live. He now sits around the house and buzzes angrily at stuff. The cats are not impressed.
Stays there, soaking the sun rays. Buzzes angrily once in a while.