I was playing Crackdown in the Shai-Gen district, I was mucking around in the street near the last boss and two gang hit squads showed up, there were around 40 gang members in a circle along with all their cars, I threw a grenade in the middle (keep in mind that my grenade skills were at 4 stars) and at that very moment, about 30 of them threw grenades, when it exploded the game went down to like 10 fps and all the cars blew up, gang members were flying as high as buildings and I was thrown back about 200 feet, the explosion was like a nuclear bomb.
It wasn't just OH forget, it was also OMG LOLOL HOLY stuff!