Late 2006 C2D iMac here. I'd probably still be using it if its GPU hadn't gone all flaky on me (random gradient fans, strange lines in windows, UI freezes). It was a nice little machine.
Before that I had a beige G3 from 1998-2006; by the end, I had replaced the hard drive, optical drive, CPU twice, RAM twice, added a flashed PC Radeon 7000 and a USB PCI card--the only pieces of original equipment left in the case when it finally gave up the ghost were the motherboard and the power supply. Shipped with Classic Mac OS 8.0, died running 10.4 Tiger.