There are so many neat tubes out there.
One by one, I will add to this list as I go through my collection.

A miniature tube with a quartz crystal inside.  Used in some early color television sets.
Rather large mercury switch.
An early 6H6 engraved metal tube with a flat top.
A tube engraved with the call letters WJAR on the base.
A Sylvania type SN4. updated! Thanks to generous feedback from several viewers, I now know that this tube is a neon filled strobe called a "strobotron", and may also be numbered 1D21 or 631-P1.  Following is a link to a very nice website with instructions for a project using this tube. Strobe project
An RCA JRC927 phototube.  Only three pins on the base.
A small 7 pin strobe tube used in precision timing equipment.
A German made 7 pin phototube tube used in early automated equipment.