We were recently exploring an old abandoned gnomish colony when we came across what was obviously a classroom for children. Desks, a chalkboard, the whole nine yards. We entered the classroom through a secret door, and when we tried to leave via the main entrance, the rogue was blasted with four consecutive frost bolt traps. Nearly killed him. Apparently these gnomes
really had an attendance problem!
Another trap which wasn't so much dumb as it was amusing was in a Dragonlance game. We were in a dungeon corridor which ended in a door. The halfling ranger was sick of getting blasted by traps, so he went back to the opposite end of the corridor and put his back against the wall. Sure enough, when the door was opened, the trap was sprung.
A spear launched from the wall behind the halfling, killing him.