Beautiful, metallic mirrors of copper or silver can easily be formed in test tubes. Simply add the appropriate metal salt to a test tube, and heat! These reactions should be performed in a fume hood.
Just the other day within my IB Chemistry HL classes, we were discussing the color of transition metal complex ions in solution. It's a bit imperfect, because they are not yet dissolved, but I set up a number of metal chloride salts in order to help students see the pattern. They are arranged according to the position of the metal in the periodic table. It ends up being quite obvious to the students that the only metal salts with color are in the d-block. I'm now in the process of ordering more chloride salts so I can complete the pattern even more the next time I teach this topic.
I am fascinated by the chemistry of pennies. I have tried several experiments found in the Journal of Chemical Education.