Riad makes some of the coolest clocks, ever – the single-digit Nixie clock is awesome and there are a couple others too. Code and schematics included – “A while ago I found a Burroughs B-5853 Nixie tube kicking around in the lab and decided that I should put it to good use. Since I only had one of this size, I wanted to make a single-digit display out of it. After I saw Jason Harper’s Nixie clock gallery, I decided that one digit really could make a cool clock.” – Link.
Weston voltmeter clock – Link.
Oscilloscope CRT Clock – Link.