I'll play.
First gun I ever bought/owned/shot/cleaned was my CIA Cetme Sporter.
Taking apart the bolt with no manual and no firearms experience turned out to be a terrible idea.
After some help from the guy I ran into (who didn't know anything about HK style rotating bolts either) I got it back together and he said to me...
"OK now never take that apart again."
At the time all I could do was laugh, as it was said in frustration rather than seriousness.
Fast forward 5 years.
A buddy picks up his first handgun, a Rugger p345.
Anyway he shows it to me, and it's filthy, the previous owner had never cleaned anything except the barrel.
Well I think I'm the king-**** of auto-loaders at the time, so I try to field strip the thing.
45 minutes later and no success, I promised the guy I would research the proper take down, but by the next time I'd see him, he'd figured it out.
....But now I give the previous owner a little more credit for not wanting to clean it.