ARAM I have two... Anivia and Ashe. The Anivia one was... odd... we were chasing all five down and I got a wall stopping them because they got blocked by a destroyed turret. I then dropped the ult (which really doesn't do all that much damage) on all five of them and suddenly, PENTAKILL. I don't even know how. They all literally exploded.
On normals, I have one... Vayne. I KSed 5 times. None of the kills were even remotely close to being mine.