Some of the coolest demos are done with very toxic chemicals and should be performed in a chemical fume hood. Therefore, some of the YouTube videos are the way to go. We will list some cool ones here.

Pharaoh's Serpent

This demo should only be done by showing this video . This demonstrations generates very toxic gases that you can read about in the link below.

http://www.sciencemadness.org/smwiki/index.php/Mercury(II)_thiocyanate