When I first got into OS X my box was a 200MHz 8500.

I still have that box, and although it has been way heavily upgraded, it will always be my first mac, and thus my first love. I will own that box until I can longer find parts for it.

First X I ran on it was 10.1.5. The OS ran kinda alright as long as I didn't run more than 2 or 3 programs at once. Once I slapped a G3 in, the machine was faster. Toss in 512MB of RAM, ATA/133 Controller, Rage Nexus 32MB and my new G4 ZIF and man that sucker flies. Currently running 10.2 Jaguar, soon to try Tiger.