I'll agree with M.W. 1, as it's one of the largest fears of the past 60 years realized, and in one way, experienced. The saving of all those people for nothing intensifies the situation.
I also found the MegaTown Nuke event in Fallout 3 equally charged with emotion (probably why they removed it from the Japanese version, if I recall correctly).
In that, the Nuclear Event watched at ("whatever Towers--Tenpenny?") akin to a person watching a sports show--humanity at it's lowest.
Both were quite shocking, and thus memorable.
As far as a "Personal Best," I think a glitch in Castlevania 2: Simons Quest was the best single moment. I walked an invisible staircase and was able to "rapid travel" through almost the entire map at the top of the screen, until a spider hit me with a web. That was 22-23 years ago, if that means anything.