You've got to go with Foley being thrown off the cell. You see a guy who's 6 ft, 300 pounds, being thrown off the top of a 16 foot cell, and crashing through a table. Who the fuck did not stand on their feet and go holy shit when that happened? I remember watching it for the first time, and I've jumped up and gone "Holy shit did that just happen?" I've done it for a video of the event, so what about the people who had seen it live?
I can't put the Montreal Screwjob, as that was more like an OMG! moment than a Holy Shit moment. The one closest to the cell throw is Hogan slamming Andre. But when its looked back on, people are like "Meh." Whereas if you look back on the cell throw, then you still go "Holy shit!" The cell throw has withstood the test of time as the true Holy Shit moment of all time.