For me it's got to be  the deadly scalpel... I will use one in a pickle when I forget or lose my wire strippers...

I can't count the amount of small cuts I've given myself or the frustration at the inability to properly strip wires and cutting through wire insulation where I shouldn't that I have done with a scalpel.

The worst case was when I blew all the fuses in my  parent's house by wiring up a wall socket with the smallest gash/cut, incredibly hard to see, on the live wire that touched the metal back box that it was all mounted within.

Fortunately it was just the fuse box and an angry dad for messing it up rather than a fire but super frustrating to find the issue when we had wired about 10 sockets that day!!

As an aside, I have messed up a fair few PCBs through hasty use of a scalpel :/

Had a weird snag on the Tornado F3 RHWR (Radar homing warning receiver) System many years ago. The loom that ran along the spine became our prime suspect, and after doing pin-to-pin checks for open circuits we had to release the aircraft back to squadron with the system 'Limited'.

A month or so later it returned to the shed for the Major Maintenance, we passed on what we had done and suggested core-to-screen checks were carried out for shorts. Lo and behold, there was one cable in the loom that was exhibiting this very issue.

Out came the Time Domain Reflectometer (screen and earth cable works very similarly to coax to a TDR) and we found the exact spot the loom was damaged. (You can see transitions thru bulkhead connectors on the TDR trace, and follow them on the wiring diagrams).

The loom was popped open and the culprit found - a beautiful slice through the outer insulation, the screen and inner insulation, with a few stray strands of screen touching the inner core . . . . . .

The culprit? The loom is knotted with lacing cord every few inches, and some deft folks were able to invert a scalpel blade between the individual wires in the loom and slice the lacing cord without causing damage.

The muppet who had done this one however had decided to saw straight across the loom at 90 degrees - he cut the lacing cord, but that unfortunately wasn't all.

We're right back to accidents (many) that I have had with scalpels, and your examples . . . . . . .scalpels are probably the most useful and, in equal measure, the worst tools to use for electronics . . . . . .

Had a weird snag on the Tornado F3 RHWR (Radar homing warning receiver) System many years ago. The loom that ran along the spine became our prime suspect, and after doing pin-to-pin checks for open circuits we had to release the aircraft back to squadron with the system 'Limited'.

A month or so later it returned to the shed for the Major Maintenance, we passed on what we had done and suggested core-to-screen checks were carried out for shorts. Lo and behold, there was one cable in the loom that was exhibiting this very issue.

Out came the Time Domain Reflectometer (screen and earth cable works very similarly to coax to a TDR) and we found the exact spot the loom was damaged. (You can see transitions thru bulkhead connectors on the TDR trace, and follow them on the wiring diagrams).

The loom was popped open and the culprit found - a beautiful slice through the outer insulation, the screen and inner insulation, with a few stray strands of screen touching the inner core . . . . . .

The culprit? The loom is knotted with lacing cord every few inches, and some deft folks were able to invert a scalpel blade between the individual wires in the loom and slice the lacing cord without causing damage.

The muppet who had done this one however had decided to saw straight across the loom at 90 degrees - he cut the lacing cord, but that unfortunately wasn't all.

We're right back to accidents (many) that I have had with scalpels, and your examples . . . . . . .scalpels are probably the most useful and, in equal measure, the worst tools to use for electronics . . . . . .