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.

Have Zeus’s lightning bolts as an item or artifact you can throw. If an artifact weapon, it should automatically return like Mjollnir; otherwise, it could be an item that vanishes after striking a target but deals immense shock damage to that target.

Wielded wood and plastic weapons (and possibly glass) block passive shock attacks, since they are non-conductive. Plastic could block 100% of the time and other materials less so, mainly to give a fringe benefit to a material that’s normally pretty underpowered.

The passive attack only gets blocked if you actually used the weapon to make your attack: if you’re polymorphed into something with a weapon attack and a bite attack, for instance, the bite will still subject you to the passive shock.

Having a copper weapon wielded while suffering shock damage has a lightning rod effect: it causes you to take extra damage, but completely protects all your rings and wands from being destroyed.

Worn rings are targeted last for destruction to electricity damage: they’ll only disintegrate if you’re not carrying any other rings to lose.

Instead of electricity blowing up your wands and rings, it makes you incapable of using rings (and potentially disables your rings’ extrinsics) for a few turns.

Add an electric trap, which zaps players or monsters who trigger it. Can also destroy rings and wands with shock damage.

Hitting monsters that have a passive shock attack with something made of copper, silver, or gold increases the amount of shock damage.

When you take shock damage, any brass lanterns you are carrying in open inventory get recharged an amount proportional to the damage taken (possibly up to only 1/3 or 1/2 of its maximum charge).

Storm giants have active and passive lightning attacks. Not sure why they don’t actually have anything to do with shock currently.

Lightning spells:

• The most common suggestion is for a level 5 attack spell that creates a lightning bolt, implemented as a simple ray. Possibly, it causes an electrical explosion on the first target it hits if cast at Skilled and Expert.
• Alternatively, a spell of lightning bolt could be a melee range spell that deals heavy shock damage.
• Chain lightning is a spell that forks off and hits adjacent targets in a breadth-first search (see here for how it might work). Possibly, the lightning bolts can only chain off at 135 or 180 degree angles (maybe 90, too). Chain lightning can still be reflected, but becomes a straight ray.
• Lightning storm, which causes an electrical explosion centered on every monster in your line of sight (possibly with a decreasing chance of doing so as it gets further from you). Or if this is too overpowered, just strike these monsters with an individual lightning bolt that does not cause an explosion.

Electric spider that, when it stands on a web, can electrify that web and all contiguous ones, dealing shock damage to anything in it.

Hitting monsters with a passive shock attack doesn’t hurt you if you’re hitting with a non-metallic weapon or your hands with non-metallic gloves on.

Dipping a wand of lightning in a pool of water electrocutes nearby monsters in connected pools of water, and possibly you.

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.

Electric attacks deal more damage to monsters in water.

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.