Solar Radiometers
If you're going to have stuff just sitting around on your desk looking cool, you might as well get some stuff that actually does something cool too. These Solar Radiometers ($36-$46) use thermodynamics invented by an English physicist in 1875 to put on a desktop show — when you set them in sunlight, the vanes inside the vacuum globes spin, and, depending on the power of the warm light, can reach thousands of revolutions per minute. Can you hear the nerd inside you screaming "Science RULES"?