I'll start it off:
I'm currently on a G4 DigitalAudio that I recently upgraded with a 1.4GHz sonnet Cresendo. Of course Max Ram and a 120GB HD. Plus, a few other tweaks. Check out my benchmarks vs. a G5 PM (benchmark is even before max ram):
http://db.xbench.com/merge.xhtml?doc1=154590&doc2=1&setCookie=trueI also have an iMac G4 700 Flat-Panel (my wife's)
And, for portable I have a G3 iBook 800 that has seen much use.
Prior to this I had a PowerMac G4 Cube 450, PowerMac G3 Blue/White 400, iMac 400 DV, iMac 350, and Performa 6300 100MHz (my first I owned)