let me start... with the most memorable ones.

growing up in the PUV business, I was expected to be able to fix my own car if something goes wrong.

1)
'91 Corolla (2E Engine) it was a normal tune-up and change oil when I lost one of the small screws for the contact point.

I found a screw that's 1mm longer to replace the missing screw. It grounded my whole ignition system which caused the ignition coil to overheat every 500 meters

2)
GF's house was a good 30mins drive (90's)

Her car's A/C retainer bearing got stuck causing her fan belt to break.

I volunteered to have it fixed (done it multiple times - our taxi fleet).

Took me 2 days to finish the job. retainer bearing's adjuster lost its thread and the bearing got so hot causing it to slightly melt. Had to bring our mechanic the next day for help.