My most aggravating: GM 10 bolt, needed to get the axles out to replace a wheel bearing. Trying to remove the spider gear axle pin when. The head of it popped off.

I ended up beating the shit out of the spider gear axle with a sledge until the remnants of the pin shattered and the axle came out.

Plot twist: I was outside and it was a rare Georgia ice storm and I had to fix it because I had to drive to work the next day :(

Most sad: screw head somehow fell out of the bottom of a q-jet and found its way on top of a piston in a Pontiac firebird formula 400. While it was spinning pretty fast. I was able to pick most of the pieces out of the head of the piston. I have them in a shot glass as a reminder. Engine was fucked

International Dt466 EGR cooler bolt, they always break off. Because of the location you have a 50-50 shot of making an easy out work. At least they are 3-piece manifolds

More of a stripped oit thread story for me.

Replacing head gaskets on a 4.9 Cadillac pre Northstar v8. Stripped the very last bolt i needed to tighten in the head when going to the 90 lbs or whatever it was. It was an aluminum block.

Ended up drilling it out  and putting a time sert there.

Shifter linkage in a 2002 focus zx3, took me 2 hrs to break it off, 4 hours of dremmeling and 2 flex shafts burnt up to get the rest of it out, then retap it(its like 3ft below the top of the motor near the firewall. Access was like5x5" once you got your arm down there about 10" of work space.) and make a part that would work.

Had a bolt off an aspire rear brake that after 3hrs of heating,banging,etc on my driveway that was a solid sheet of ice i gave up and took it in.  Took the brake guys 6hrs to get it off, guy wanted to keep it as a trophy. IIRC they welded 2 or 3 nuts to it to finally get it off.

I hate working on cars with a passion.

Muzzel brake on my noveske broke 2 armorers wrenches and the shop gave it back to me and said to bring it in in a week when they got a reaction rod...lol.

Broke a head bolt off a seized pressure washer engine.

I've shot parts out the cover of a GM 8.5"/10-bolt

That really looks like the bolt was only ~30% closed.

ETA: It's interesting to see the hammer pin is out.  To bad it's not on video where we could see whether the pin was out before he closed the bolt or if it happened during the bolt failure.

Jeep cherokee with shocks rusted so bad we ended up cutting the shock stud off and using a large bolt and nut to mount the new shocks.
That was after my boss decided he could beat the shocks off with my bfh and ended up destroying a few more brake parts with wild swings that we replaced for free.

71 gto with a 400 in it.
thought I had dropped a carb nut into the intake. Well not me ,but someone.
So we tried to pull a head off to take a look around.

Literally used a 6 foot cheater bar and it would not give.
popped 4 sockets before we gave up.
That is right, the sockets broke at the weakest point and would not hold under the force we were putting on it.
even bought a snapon thinking it might be stronger, it too died.
never did get it off, found the nut in the trash in the valley pan.

The guys at work call me the heli-coil king.

I had an C15 come in where every exhaust and turbo stud broke off. Salt trucks will do that. I like the burr bits they sell at machine tool stores. Thy let you get a good center o a broken bolt and you can drill from there. I don't use extractors or ezouts. I've seen too many break off.

If you drill all the way through the bolt and then soak it in penetrating oil and go up 1/16 in size at a time you can usually get the bolt to break free and then walk it out with a left hand bit.

Takes time and patience.