Potassium and sodium would make quite large explosions. Our chemistry teacher in high school would sell us small amounts of Na+ and K+. We would hold on to it until we had enough to make a larger bomb, so as to have a larger blast. It all stopped when someone flushed a large quantity down a toilet the lower building and blew the fixture off of the wall. The teacher was not fired because no one would say what the cause of the explosion was, but he knew and would not sell us anymore after that.