A damage type that shuffles around the player’s intrinsics, never taking any away for a net loss, but always rearranging them, so you could lose fire resistance but gain teleport control, or lose telepathy in exchange for intrinsic protection from shape changers.

Special damage type AD_GNAT: when hit with it, you are compelled to attack the offending monster on your next turn if able. (Or as a weaker version, you can do things other than attack, but if you want to attack you must attack the offending monster).

Not specified what would happen if you are hit by two gnat attacks on the same turn.

Disfiguring poison that drains Charisma.

Add the “necrotic” damage type from D&D, so that evil monsters can deal corruptive or decaylike damage without resorting to instadeath, level drain, or disintegration.

Add a new damage type AD_CHOK, for specific suffocation attacks (so that rope golems’ AT_HUGS AD_PHYS combination doesn’t have to be interpreted as choking).

Vampires drain levels much less than they currently do, or not at all; instead they use a bite with an AD_DRHP damage type (described in #1627). Possibly give vampires one AD_DRHP attack but let vampire lords keep one AD_DRHP and one AD_DRLI.

Monster or damage type that un-erosionproofs gear, not very common.

Mosquitoes, an a-class monster which uses an AD_DRHP attack, which replenishes the mosquito’s health by some fraction of the damage it dealt you.