Well I was
GM once when the players, 3 of them, were defending a vox-tower on top of a hive-spire from a insane gang of khorne cultists.
The cultists had to fire and charge across a narrow bridge and the first one to charge had a suicide-vest. He got his leg shot of.
And the second one, and the third one, and so on, kept getting their legs blown apart or they stumbled to the ground in some dumb way and eventually the whole bridge was piled up with 10-15 dead or wounded cultists.
Eventually one
pc shot the crawling suicider in the chest with a lasgun, ignited the vest.... and well, boom. The macabre idea of his vest exploding in a pile of 10-15 cultists made us all roar with laughter.
They were a bit less happy when the bridge fell apart though.
On the more epic side, one group of players sort of partially by their own guilt and stupidity, cleaved a space-hulk in two above a planet. A spacehulk used as a space station, populated by a few million or so people. So yeah, oops.