Underneath the PF you are generally OK - your main worry here would be shorting something out and blowing a fuse or taking a component(S) out on a board.

Wih PF up - the serious concern is inside the cabinet itself - main on/off switch, feed to transformer etc. Even with game switched off at cabinet swtich you have live wires here. Always best to turn off at the wall socket.

I always try to work one handed when inside the cabinet, especially if im poking about testing voltages at fuses etc. That way if a i do get a tickle it doesnt flow across my chest and heart and out the other arm.

Interesting you should post this. i recently replaced the power board to spiderman, switched game on and she didnt work. Whilst pondering on the problem, i rested my hand on the top of the open door and got a mighty shock. This one bit! I could still feel it in my hand some 1 hour later. But!!! The other hand was in my pocket and so current had nowhere to flow.
Dangerous i know, but it did solve my problem - there is NO earth on this pin at all - all ground braid has been removed. You know, i never thought of checking first, mainly because i cant believe someone would be so stupid to do this in the first place.

Lesson learnt...