I know no one really cares about core mechanics cause they don't make a game.
But mine is based around d10s.

You roll 2d10+adds, mostly just skills, against target number. 12 is the default since an 11 average would fail thus meaning that first +1 in a skill makes the most difference in making you succeed. I don't like it cause it's kinda inelegant. Before I was using 2d8 (average 9) against average TN of 10, which was the same, but a more elegant base TN (nice round number) but smaller number range.

The second part of this is the damage mechanic. You roll 1 to 3 d10s, depending on weapon used, and each one that rolls equal to or higher than their Armor scores 1 Wound. Unarmored is 6, light/medium/heavy are 7,8 and 9, and 10 is reserved for truly impenetrable legendary monsters (because it's twice as good as even heavy armor).

So a guy with a greatsword hitting a guy in chainmail (Armor 8) would roll 3d10, getting say 3 7 and 9. The 9 would deal 1 wound, the other two would do nothing.

Most enemies would only have 1 wound. Characters start with between 3 and 6 they can take before going down. The point here is low-bookkeeping without sacrificing more in-depth encounters. Might allow 2 wounds for "mook" types instead of 1, so they can be "wounded" which is pretty easy to track.

This is for a game that is going to be focused on domain-level play, but also in depth alchemy systems, rune magic systems, and lots more. So it's important to be able to handle mass combat but also be able to have a good system for high-health enemies.

I had the same thing with 2d8s system but it was harder to have "room" for all the armor types when Unarmored was 4 and then 5-7 were for the 3 levels of armor.

So essentially I liked the 2d8+adds better for a resolution mechanic. But I liked 2d10 better for the damage mechanic.
And I want this game to only use one type of die if possible. Dunno if anyone actually cares about that though.