One of the worst is when you're working on an EM, and you drop some minor little thing like a nut or a bulb or something... and it lands just right to slide down beside the board on the bottom of the cabinet, then roll under the board so you can't possibly reach it.
So then you have to start thinking "Should I try to just tilt the cabinet to one side and see if I can get it to roll to the side and grab it with some pliers?"
or "Maybe I can slide something flat under the board and push it out the other side"
but eventually you have to take the bolts loose and move the board to get whatever little tiny thing you dropped down in there out...