One of the most
irritating traps in
NetHack is the beartrap, because if you step on it, it
clamps onto your
leg and you are unable to move off of that square until you manage to
struggle free. Needless to say, this seriously jeopardizes
escape attempts or planned
raids on
leprechaun halls (I had this happen once, it was an incredible
fiasco). By far one of the most
annoying things about beartraps in
NetHack is that they are re-armed after you
escape from them, meaning that if you aren't careful, you can get stuck in it again.
As of the latest versions of NetHack, you can use the #untrap command to disarm a beartrap. You will then be able to pick it up and carry it with you -- I usually don't because they weigh in at 200 (that's several broadswords' worth). You can drop the trap and apply it in order to arm it. I don't think I have to tell you what happens if you try to disarm a beartrap and fail.
If you aren't carrying a whole lot of stuff or have a high Strength score (or a devious plot), it is very amusing to trap monsters, especially nymphs, in beartraps. You can jump or levitate out of a beartrap, but such forcible escape from a set of iron jaws can cause enough damage to kill you at lower experience levels, so be careful.