Adding to houses and cars, old industrial machine tools, particularly those with any electronics in them are worse. Even more fun is that the simple act of moving them from one place to another often breaks the electronics.
On bicycles:
A quick derailer adjustment, but the cable is too short and someone cut it off right after it attaches. Undoubtedly the chain is also severely worn and the derailer hanger is bent.
Aluminum seatpost stuck in a steel frame. Even better if it was all the way down when it got stuck.
Going in for “the cones are just a bit loose” on an old freewheel rear. It feels like the half the time the axle isn’t bent is because it is broken and the QR was holding it together.
Anything involving wheels that have been commuted on through a winter.
Quick tube change for a friend, and once the tire is off there is no rim strip and the spokes are long enough to be poking up into the tube.
”I need my brakes adjusted” is code for “My rim
is so bent you won’t be able to true it out.” This when the wheel doesn’t have broken spokes and is improperly dished.
Any thing involving the phrase “it feels a bit funny” and an old Vitus bonded frame.
Need to adjust a bottom bracket and finding out the extractor threads are stripped on both sides.
The first time you need to replace a BB cup on a 70’s French bike.