My favorite game hasn’t always used an icosahedron as its core mechanic. Even the much loved “roll a die, add some math, roll higher than a number (either flat or as generated by a similar procedure) is a relatively modern invention.
The original skill mechanic is OD&D’s “Secret doors are spotted with 1-in-6 probability” rule, a humble six sided die.
Attack rolls were from chainmail and were 2d6, as were morale and encounter and turning checks.
The DC system comes from turning THAC0 on its head, by way of Rolemaster (which was an earlier version of d20 on a percentile system…).
So, my point is, we don’t need to love the d20 as much as we do to say we’re playing D&D. The funky polyhedra are our shibboleth, our shared sign, our password into geekery.
I’ve been playing* Zombicide with Andres and struck by how elegant its weapon system is.
Here’s the relevant bits:
All of the dice are six sided.
A very blasty, swingy weapon gets lots of dice, up to five-ish.
A very precise, certain weapon counts wider ranges of numbers as hits.
One success die equals one dead zombie, generally; special zombies take progressively better weapons (but the statistical properties of those überweapons are similar to non-über; it’s just a special permission bit).
I think this is so cool: imagine a spear (1d, hits on 4+) vs a battleaxe (3d, hits on a 6). The spear is 50% likely to damage on a hit. The axe has a higher probability of not hitting anyone, but can sometimes hit 2 or even 3 hits.
I’m not sure about weapon’s überness; maybe that’s magic weapons.
The player can determine internally their possible damage total without reference to the DM. Bam, 2 hits.
Downsides: hit points and damage and armor class and situational bonuses.
Those are hard. I think you lose all of the benefits if you require the defender to tell the attacker to modify their attack or use different dice or whatever, so the defender pretty much has to let the attacker completely resolve and then react. Technically, you could have the defender modify the target number for a hit, but that’s awful complicated.
One way you could deal with this is to let armor increase toughness (like: chain armor absorbs 3 hits per round). You could also let people parry or dodge to negate entire attacks or hits of damage.
The really great thing about this is how well it scales into a wargame — 10 guys attacking? Die-pool time, but resolving the attacks isn’t very hard.
* the present pluperfect hides an awful lot of geography.