Ok, so it's not really a robot, but this little "pretend robot" would be fun to try to build nonetheless. The website I Make Projects.com has a neat project on how to make a mini robot sculpture. Like this quote from the person who put up this project, see what monstrosities you can make. Follow the link by clicking on the small photo for more information.
"One day I took some of the parts and soldered them into what I wished was a functional spider robot – but even though it didn't work, it was pretty in its own way. It was also fun and inexpensive and fast to make."
All you need to make the one shown which is a spider bot is some capacitors and resistors and a small chip. Well, if anything you could practice some soldering and have a little spider bot to keep you company, or a cool Halloween decoration.