The Amiga, after all the frustrating moments I've had with her. PCMCIA pin breaking (Grrrr), hardware not working, annoying software quirks, hard drive weird memory errors. The crashing, the conflicting hardware.
The unstable nature, one day working the next not. Silly little niggles. The more pain in the ass it gets the more you upgrade her.
But at the end of the day, I still come back to her, still curse, still jump with joy when it works.
Priceless.