Cody's Lab. He has been building a Mars base in the Utah desert for a couple of years now, including not being able to work on stuff without a "space suit" or Robo Cody. He also does a lot of very interesting science experiments involving chemistry, engineering, and geology.
Styropyro. Very hard to describe, seriously just watch one of his videos, your mind may be blown (by lasers or very large battery arrays, who knows!)