One of my first ever DMs ran an adventure where an NPC walked up to one of the PCs and said, "Excuse me, I'd like to eat you horse." We were all 1st level, so naturally the player was pretty possessive of his horse, and freaked out. The NPC turned into a gold dragon, ate the horse and the PC, and flew away.
Another time, we played with a complete novice DM. He uttered this phrase which has achieved immortality in our group as the benchmark for poor DMing:
"You hear a rustle in the bushes: six green dragons jump out!"
Oh yeah, my character killed the last Gobbledok, as well.