PowerMac G4 Digital Audio with 1.5ghz OWC Mercury Extreme upgrade, 1GB
PowerMac G4 Dual 450mhz upgraded to 1.5ghz OWC Mercury Extreme, 1GB
PowerMac G4 ??? with the old 733mhz from the Digital Audio, 512MB
PowerBook G4 "Q16A" (pre double layer)1.5ghz, 15 inch, 512MB (what I'm using as I type this)
I skipped G5 and now I'm ready to buy an Intel Mac, I'll definitely get the Mac Pro and maybe trade the powerbook for a macbook pro.
All of those machines have been extremely reliable considering I got the first two when they were first released and they run Tiger like a champ I'd say they were pretty future proof compared to my PC from 2000 which was pretty slow at the end of its days. The other machine with a 733 and 512 RAM is very slow but very usable even in Tiger, this PowerBook would be golden with 1GB RAM (512MB makes machines slow at least in Tiger) but its already fast enough for what I do in this laptop and I don't want to spend money on a machine that will probably get the boot very soon.
I'm on a 1 Ghz Titanium powerbook with 1 gig of ram and will upgrade the 4200 rpm 60 gig hard drive to a 120 gig 5400 rpm hard drive soon. This machine is so gorgeous that I'm going to try to wait it out through leopard with it. All I have to do is add a usb 2.0 pcmcia card and I'm set for the moment
my parent also own a 667MHz TiBook, a (dead) 800MHz iMac G4, and a 1.83GHz MBP, but I take claim to ownership of all of them (except for the iMac, which is now my property of my parents so they can pay for repairs )