Shock resistance (possibly only extrinsic shock resistance) prevents you from being paralyzed by a ghost’s sudden appearance even if you lack free action, because you are resistant to being (emotionally) shocked by things.

Shock resistance turns ‘!’ at the end of in-game messages into ‘.’.

New artifact Bolt Boots, jumping boots made out of copper or metal. Conveys shock resistance when worn. Does double damage on kicks, which is treated as shock damage that may destroy rings and wands in a monster’s inventory.

When jumping with the boots, you may pass through monster’s squares (but still have to land on an open square); any monsters passed through will take damage as if hit by a wand of lightning.

Artifact ring that provides a cocktail of basic resistances all at once (fire, cold, shock, poison, maybe sleep, maybe acid). This is interesting primarily because it is very useful early in the game and then becomes progressively less useful later on as the hero gets intrinsic resistances.

Could be named “The Ring of Everything Resistance” or “The Chromatic Ring”.

Amulet of Storms, an artifact amulet of flying that additionally grants shock resistance when worn, and allows you to pacify true v monsters (i.e. not alternative forms of other monsters that happen to be turned into a vortex as a defined alternative form, such as vampires and the Wizard of Yendor, but counting shapechangers such as chameleons) when chatting to them.

Divine lightning (a god smiting you, particularly Moloch when you attack his high priest) should ignore reflection; it’s a “wide-angle” blast of lightning. Maybe this should apply to the lightning monster spell too. The high priest of Moloch should also be shock resistant.

Proposed nerfs for ring and wand destruction due to electric damage (some of them extensible to scrolls, spellbooks and potions for fire and cold damage):

• Rings never explode, as they are rarer and a more crucial part of a player’s gear. Only wands explode.
• Wands and rings made of metal never explode.
• The amount of wands and rings that can be destroyed by a single shock attack has a fixed cap. (Currently it has no cap and everything can be destroyed if you’re unlucky.)
• Extrinsic shock resistance (and only extrinsic) protects against these effects completely.
• Wands and rings hit by electricity act similarly to being charged, though they don’t actually get charged. Wands have their recharge counter incremented then roll for explosion. Chargeable rings roll for explosion at their current enchantment (meaning +0 rings will be safe). Not specified what should happen to unchargeable rings; perhaps they should just behave like +2 rings or something.
• The maximum number of items that will be destroyed is the amount of damage divided by 10, so an attack dealing less than 10 damage will never destroy anything, and e.g. a 6d6 damage attack from a wand will destroy at most 3 things. Combined with a possible hard cap of 5 or so items per damage.

Mjollnir confers shock resistance.

Change the message for gaining intrinsic shock resistance to be “Your current health feels amplified!”

Boots of shock resistance, which have a thick rubber sole to prevent you from being grounded.

Note: several other people have commented that since such boots would prevent you from being grounded, you would actually take extra shock damage from other things, like touching grounded metal objects.