I absolutely hate these moves. They are terrible when you use them, but computers have extreme luck, so it's an OHKO.
I usually encounter Rhydon with OHKO moves when I'm training at Victory Road. And of course it always hits, so I have to go back to the Pokecenter, try again, and hope I don't find another. It would be fine if I wasn't trying to train, but since there's no other reason to go there...
Then there's Pokemon Mystery Dungeon, where Perish Song can be considered as one. No switching, no escape, no questions. It's an automatic death.
>.< Like I said before, I hate these moves.