Here is a Nixie Clock from Nixie Neon that is a little bit usual. Instead of using solid state components to provide the counting logic, it uses a tricky piece of circuity called a "ring counter" to divide the input mains frequency down to pulses that drive the Nixie tubes.
Originally this was spotted as an eBay auction, starting off as a $0.99 auction. It is certainly one of the more innovative Nixie clock designs that I've seen (innovative in that it is unusual to see the logic done this way nowadays.
Have a look at the video below to see the ring counter goodness. The spinning neon lights are NOT decoration, they are the logic to run the clock!
From The Auction
This kit has all of the components to build a unique clock utilizing neon ring counters to countdown the AC wall current. The kit includes the front and back pieces of plexiglass, the AC adapter, PCB and all electronic components including spare neon bulbs and fuses.
The completed clock is 7 1/4" square and 2 1/2" deep.
The clock can stand on it's own as it is, or it is ready for you to put it in the case of your desire!
With over 400 components, it will prove a challenge for young and old electronics hobbyist.
The kits include BLUE neon bulbs marking the 12, 3, 6 and 9 o'clock positions.
To view schematics, the assembly manual and other good stuff about the clock, visit http://www.nixieneon.com .