Best idiot trap?

[Roninblack]

There's a reason that Tomb of Horrors, a dungeon based around cheap and hard-to-detect traps, is the least fondly remembered of the classics.

I'm gonna second this as not sure that's true. The trick is to understand the purpose of tomb of horrors. My understanding is that Gygax designed the tomb of horrors as a way to challenge the players and not the characters. Hence any number of dumb choices get people killed and your class or feats no way help.

He would pull out the module when someone said ex. My ubercharger barbarian is unkillable, it cannot be defeated, I have won D&D. ToH is designed to make "unbeatable characters" cry, because the players are beatable, even if the character isn't.