I can't say I owned it (it was my dad's) but I lived with it for many years and got very experienced at repairing it.
1988 Pontiac 6000
Got to replace warped brake rotors frequently, and the self-adjusting rear drums would occasionally not self-adjust.
Cooling fan motor went out at 50,000 miles or so, but since it only had an idiot light we had no idea it was running hotter than usual, and it apparently never got hot enough to turn on the idiot light. The only symptom we had was the air conditioning cycling off, and when the compressor kicked in it shuddered like you just put it in gear.
It seemed to go through ignition wires and spark plugs at a good clip, and since it had no knock sensor it would ping like crazy if the wires were going bad or the plugs had eroded themselves from .060 to more like .080.
The tensioner bushing would get worn, and the idler pulley would get cockeyed, then the belt would start rubbing the engine block. Strangely, the dealers could never sell you the worn out bushing, but they did have a copious supply of idler pulley assemblies, and once you said "2.5 liter four" they knew exactly which one you were talking about. Since it was this big aluminum casting which included the power steering pump mount and the front cooling jacket cover, it was never a simple and always messy job to replace.
Blower motor went out one winter, although that was just because the cheap connector at the blower motor wasn't well protected against the elements. A little steel wool fixed that, but it was cold for a few days until I could find out what was wrong.
The plastic timing gear let go at around 100,000 miles. Although I can say that was the only time it left us stranded on the road. Still a chore to replace it though. We took that opportunity to replace the steering rack which was having a severe case of morning sickness.
The thermostat started opening too early, but it never turned on a "service engine soon" light. I figured it out because the torque converter started dropping in and out at odd times. Once I noticed that it coincided with the heater warming up and cooling off noticeably, got that fixed.
One half of the ignition module started getting flaky in cold temperatures, so one day it flooded trying to start it, and for a week a buddy of mine and I were trying to jump start it. Finally got it running and got it to the dealer to diagnose it.
One of the silly problems it had was when the rubber bumper for the parking brake pedal actually wore out, the pedal came up too far, and slipped off the warning light switch. Parking brake released, but the BRAKE light was on. The next time I put the parking brake on it broke the switch arm off, and the BRAKE light was on all the time. The dealer looked at me funny when I was ordering a new bumper pad and parking brake switch.
I think it had about 180,000 miles when I gave it back to my dad after I graduated. It soldiered on for another year or so before the headliner started drooping and the transmission wasn't shifting right. During the last week I was still driving it, it managed to shed two hubcaps on the road, and the alternator quit for the third time.