It gets old fast, but every few months I'll turn on Rainbow Road / Cowbell and it makes me smile.
(If you don't "get" the cowbell easter egg, see https://www.youtube.com/watch?v=cVsQLlk-T0s)
The one I see every day happens because I named my car 42.
However, my absolute favorite, and I use it frequently, is "Keep Summer Safe" (if you don't understand where that comes from, see https://www.youtube.com/watch?v=E2uCbXUmpZY).
Monty Python egg
How to access Cthulhu?
Old school, so drawing on it with the clear crayon before dipping it to create a cool image or message