This impresses me to no end. Not the Nixie clock, though that is also very cool. I'm talking about the HomebrewCPU. This thing is insane. Bill Buzbee designed, and built this entire thing using only 74 series TTL chips. That's a jump up from just using straight transistors, and diodes, but not very much of a jump. Check out the kinds of things available in the series, and if you know what any of that means, you know that the ICs provide only a modicum of ability above straight transistors - the ability to compare 2 bits, shift them somewhere, invert them, etc.
On top of that, then he built a compiler for it, and a beautiful front panel of switches, and blinky lights. The whole thing is wire wrapped, too! It's just insane, and amazing.