Cleaning pins on an IC
Used the wire brush on the Dremel
Naturally a short circuit on powerup

Ditto the dremel wire brush. I was cleaning metal ball guides on the PF and had a row of lights short out on the next power-on.

Worst mishap was on a kiss cpu board. I was repinning the lower left connector. 2 grey looking wires got them mixed up. I sent 40vdc to every pcb and blew them all out including displays and even sound board. Besides a couple miswired coils over almost 35 years not too bad..worked on 7000 or more games

Pulled a through hole, which I solder stitched and was fine afterwards?

Not very exciting, I guess....though there are currently like 6 balls in the subway of my project No Fear right now... LOL..

Figured out Windex isn't good for original mint 1968 pop bumpers, luckily stopped before it took too much off but still not right and I cringed at myself for a solid few days

https://pinside.com/pinball/forum/topic/hate-those-little-mistakes-that-you-cant-take-back

Being intoxicated, tired, or somewhere between..... hooking up power supply wrong to a board has happened more than i'd like to admit. Most recently i was game testing a Bally -32 sound board that needs 43v to power the amps. Game testing in Black Pyramid I typically set the board on the PF glass and use a test harness i have made. I had the power aligator clip test leads to the sound board proper, but I plugged in the not keyed(derp fixed that later that night) 15 pin test connector upside down. I sent 43v to the solenoid driver board 74154 decoder which promptly exploded.

very first game I owned, before I knew anything about pinball, I did the following:
1. Tried to fix a flipper needing a simple rebuild by first spraying WD40 all over the flipper mech
2. Item 1 didnt fix it, so I thought maybe the flipper was catching on the mylar, so I removed a small piece near the bottom of the flippers
3. Item 2 didnt hold long at all and then the mylar starts peeling
4. Decide, screw it, ill just take all the mylar off
5. Item 4 failed miserably and I end up removing half the paint on the playfield

Man, that was a lot of failures. Good thing it was just a Gottlieb teed off that I didnt have too much into. I jacked it up so bad though, I ended up just giving it to one of my pinball buddies.

Suffice it to say, I then went and spent months learning everything I could about pin repair and didnt touch another game until I felt confident I was actually doing the right fixes.

Put a set of plastics in the oven to flatten them on low heat. Was watching closely, took the tray out as soon as I saw them start to flatten. Didn't realise our oven has a hot spot in the back right-hand corner and the plastics there were nice and frothy looking. DANGIT!

all of these were my FML moments:
1. Screwing a post down on a clearcoated Xenon playfield and the screwdriver slips and into the clear it goes, leaving a nice + dimple next to the alien chiks face
2. The previous asshat left a bunch of metal tags on the display connectors on a TAXI, I took them all out but one that I did not see (nestled nicely under one of the displays). Turn the game on, and poof magic smoke. Very hard to find display board gone.
3. Machine sanding a playfield flat with 600 grit and Naphtha. A sliver of metal was buried into the orbital rubber bad, causing little circles ALL over 1/3 of a playfield area.
4. Standing a pin on its back with the hinged head not strapped onto the lower cabinet yet. Wham.
5. Storing a restored lower cab in my shed (on its back), and befriending a feral cat. Cat decides to go in and mark its new territory *repeatedly* on the said games back panel.

That's sucks. I never even thought of that. I have cooked a ton of plastics and I am glad this wasn't the outcome

First time cleaning a translite (TZ) and thought Fantastic would be the perfect cleaner to get rid of all that brown grime. It sure did - along with all the white blocking/masking paint

I lost control of a hand truck and dropped a Spider-Man down a flight of stairs. The hand truck put a hole in the wall the game was totally on it's head. Amazingly, I had pinball armor on the game and the game was basically undamaged.
When it dropped I thought I had completely destroyed it. One of the worst moments of my life.

I somehow got superglue on my Stern batman machine, when I got it off, there were a lot of scratches, did some research, found a turtle wax clear coat repair kit, used it, did work pretty good, but not all areas were level, especially the Batman in front of the flippers, got my bottle of rough cut and buffing pad and drill, and though I could even it out, when I lifted the buffer up, half of Batman's face was GONE, I walked away saying it did not happen, it did not happen, went back to the game, it happened, and this was a low play home use only game.. Got a replacement playfield from another pinsider, then did a full swap on it... I have other stories, destroyed a CPU board, and several others.. But the Batman was painful, think I paid 550 shipped for the new field, and sold the damaged one for 150 on Ebay, minus the fees and paypal fees, so figure 130 I got for it, nice 400 dollar and 30 hour swap over lesson. I probably win this contest, but I guess winning makes you the biggest loser in this case.

Wow! And I thought slamming my play field down and rubbing the paint on side of the inner cab was bad.
Whew! Amazing!