Ok a bit of double cross-posting here. But I'm liking this topic a lot. Neat.
But before I send you off, one thing: Again - I honestly think that traps should be done with subtlety just as magic should be done. Over doing it is not a good thing. Characters should not be confronted with traps just for the sake of throwing traps at Characters. They should always have a purpose, a history, a plan, and a story around them. Maybe many. Ok, we're off!
After you read this:
Tricky, Nasty, Low-Down, Stinking Dungeon Traps!
Dungeons: First Pass
Dungeons: Tricks & Traps
Dungeons: The MurderHole
Here's a few more:
* Bugbears in the ten foot pit is not bad
* The gargoyle's head with open mouth on the wall, with a Sphere of Annihilation in the mouth.
* Ye old sliding floor to the third level. sheesh. who can forget that classic?
* The ol' Lurker Above is always classic, as is the Gelatinous Cube
* Ooh, the two guards protecting two doors. You know, that whole "one tells the truth, one lies" thing. Except they both lie all the time.
* Traps which go off ten feet behind their trigger.
* Open the front door of the dungeon and it drops you into a prison cell
* One favorite from Master Davids World: There was a long very narrow corridor at the end of which was a square stone chamber with a chest of gold in the middle. In the room is an invisible six armed cave troll. We didn't know what happened when the thief got lifted into the air and rended into pieces the first time we found the place. Just up he went and scrueeench... eventually we figured out what it was. So we put up a sign "Warning: Invisible Cave Troll". Later we wound up back there. The wizard of the dungeon turned the sign invisible.
* He had another room of sliding stone pillars that were intelligent and hungry.
Note: The thing is with David's world that you had the feeling that the traps were not there as devices to muck around with Player Characters. They had the feeling of some other deeper purpose. There was a sinister underlying motif which had to do something with the ancient lost races and their doings... it was pretty impressive