I had a job where I had to do QC on discs roughly the size of a silver dollar. For them to be usable, they had to be extremely flat and of precisely the right thickness. I sat there for hours on end beside a marble block with this needle used to measure the thickness. I had to take several measurements per disc and enter them into Excel. Every morning I contemplated quitting by just not showing up the next day. Thank God I don't do that anymore.
Doing a physical inventory is another job that brings up suicidal tendencies for me.