Many traps that do damage will do more damage to the player if they're generated deep in the dungeon, which means arrow traps and suchlike are no longer meaningless to high-level, high-HP characters. Also, some traps can randomly disappear if players or monsters trigger them repeatedly.
^ Web traps display with the "^" glyph to avoid confusion with amulets.
^ heap of shit, which is hazardous for players by doing d(4, 4) + rnd((level_difficulty() / 2) + 1) points of damage (less if acid resistant), possibly damaging the player's worn boots (lower chance if they're erodeproof or of a type that can't be eroded, but it can still happen). There is a 5% chance for the player to lose intrinsic and non-permanent extrinsic speed, and a 10% chance (1% with free action) to be paralyzed for rnd(10) turns. However, monsters triggering this trap are experiencing no harmful effects; instead, they speed up if they weren't fast already, so it might actually be a good idea to displace a pet onto a heap of shit. Flying or levitating players won't trigger this trap, and there's a 2% chance for it to disappear if a player triggered it as well as a 5% chance for it to disappear if a monster stepped on it.
^ spear trap (from Sporkhack), doing rnd(10)+ rnd(level_difficulty() + 1) points of damage to the player. A player polymorphed into a thick-skinned monster removes the trap without taking damage, and a levitating character or one polymorphed into an unsolid monster doesn't take damage either.
^ ceiling collapse trap (from Sporkhack), which can be triggered by the player only and also triggers only once, dropping a shower of rocks and boulders on the player. Up to 200 rocks/boulders are generated, each of which adds to the damage taken (2% chance for each to be a boulder instead of a rock), and the ones landing on the player's square do 0-1 points of damage (+2d4 if a boulder). If the player is wearing a hard helmet, the damage is divided by 2; however, rnd((level_difficulty()*2) + 1) points of damage are added to the final damage done to the player. This means a player character who is low on hit points already may be killed instantly by walking into this trap.
^ ice trap (from Unnethack), doing d(4, 4) + rnd((level_difficulty() / 3) + 1) points of damage (less if cold resistant) to a player walking into it, with a 10% chance of the player being frozen for (5 * damage taken from the trap) turns and a 1 in 33 chance of shattering potions in the player's open inventory.
^ magic beam trap (from Sporkhack), which fires a random beam at the player or monster triggering it. Possible beam types are magic missile, sleep ray, lightning bolt, fire bolt, cold bolt, poison gas, acid ray, solar beam, or death ray/disintegration blast. There is a 5% chance for the trap to disappear if a player triggered it, and a 14.3% chance for it to disappear if a monster triggered it.
^ rust trap, rusts some items when the player triggers it