That Lego Table Top Thing *
* Sorry, I forgot what I named it.
This was my entry into the Fall 2006 Table Top contest. It's pure Lego-NXT. It goes to the end of the table and back (without falling off!) and waves a Chibot's flag on it's way back while repeating "Yipee!". It got a perfect score, but came in fourth in speed. This motivated me to buy bigger wheels.
There are build instructions on Flickr here.