I've been meaning to do this for a couple of years now. Nixie-tube house numbers. But houses don't move (often), so you really only need one digit per tube. Plus, you need it BIG.
Thanks to Portland glass artist extraordinaire Andy Paiko, who owed me a favor after I built some microcontrollers for an installation he did with local musician Ethan Rose, I had some Nixie-looking glass tubes that fit into 2.5" PVC couplers. If you use a little imagination, they look like big Nixie envelopes.
Add some EL wire (ELLumiglow.com) and you're golden. Or orange, actually. But I'm thinking it'd be REALLY cool to have actual neon tubes in there. I'll have to take the project around to a sign shop to see what they can do.