I am curious what are the 1 or 2 best, must-do demos that you do when you teach inorganic chemistry?  My students love demos, but they do take a lot of effort to plan for ahead of time, set up, and then clean up and dispose of afterwards.  The "culture of the last minute" is my typical M.O., so I tend to only do the tried and true demos that work and are both impressive and educational.

Here are my 3 that I always do in my sophomore level inorganic course:

1. Liquid oxygen