I've been at this for a while now and I've yet to come up with anything really good. The oldest one I used had a momentary unconsciousness effect. It didn't work out so well, because it was delivered directly as an interaction, rather than through material syndromes. So, the interaction would take place every time the game loaded a new area. An adventurer struck by lightning once in their life would spontaneously fall over and take a ten minute intermittent nap every time they dropped out of travel mode, for instance. The cycle could not be broken.
Right now, I deliver it through a material syndrome. This is the current version:
[INORGANIC:SPELLCRAFTS_ELECTRIC_LIGHTNING_INORGANIC]
[USE_MATERIAL_TEMPLATE:SPELLCRAFTS_ELECTRICITY_TEMPLATE]
[TILE:'#']
[STATE_NAME_ADJ:ALL:lightning]
[STATE_COLOR:LIQUID:WHITE]
[STATE_COLOR:GAS:WHITE]
[DISPLAY_COLOR:7:0:1]
[NO_STONE_STOCKPILE]
[SYNDROME]
[SYN_NAME:Electrical Shock]
[SYN_AFFECTED_CLASS:GENERAL_POISON]
[SYN_IMMUNE_CLASS:LIGHTNING_IMMUNE]
[SYN_IMMUNE_CLASS:SYNTH_IMMUNE]
[SYN_INHALED]
[SYN_CONTACT]
[CE_PARALYSIS:SEV:100:PROB:60:RESISTABLE:MUSCULAR_ONLY:SIZE_DILUTES:START:0:PEAK:1:END:5]
[CE_DIZZINESS:SEV:100:PROB:100:START:0:END:20]
[CE_PAIN:SEV:100:PROB:100:BP:BY_CATEGORY:ALL:VASCULAR_ONLY:START:0:PEAK:3:END:20]
[CE_BLISTERS:SEV:100:PROB:100:LOCALIZED:START:1:PEAK:40:END:50]
So paralysis, blisters, pain, and dizziness. The material template is liquid at 1 urist, and boils at 2 urists, so it effectively explodes the tick after contact. It's dispersed as a liquid glob, so as to be effective at range. And also because, as a vapor flow, it would have a higher chance (near 100%) to infect the caster than the target unless literally on top of them, and material syndrome immunities apparently don't recognize interaction syn_classes, or something. For instance, if LIGHTNING_IMMUNE is a SYN_CLASS added to the caster by the interaction or syndrome that gave them the spell, they don't get the immunity, but if it's an inherent creature class, through the [CREATURE_CLASS:x] token, they do. So, I've only been able to create an immunity the creature doesn't already have by going through a transformation into a creature that is immune, which isn't ideal. I also used a web spray in one test. Again, not good for the caster.
This doesn't cause any direct structural damage to the target on impact, just the syndrome, which is often fatal due to the paralysis in adventure mode. Might not want it set that long?