I've got 3 at the moment:
1. Visions in Xenoblade 1. So many RPGs have the "oh no the enemy is charging an attack, time to defend" which eventually gets old if used too much, but in combination with the topple system, this really stands out. It can come up with many enemies and they don't even have to be story related, and it shakes up strategy to either topple the target before the vision comes true, change its behavior in some way to do something else, or just let it happen since you know the attack won't be that big of a deal.
2. Rewarding taunts. No, not multiplayer taunts. Ingame taunts usually are a fun addition that does nothing, but in games like Bayonetta where it increases points at the cost of faster enemies is so much more interesting. Also, it helps with catharsis if you get through a tough section
3. Hollow Knight. This is a minor spoiler but since the game is still new -
Overcharming. Just like purposefully unfixed exploits are left in for speedrunners, the IDEA of the player "breaking" rules for a price is so interesting. It's even cooler that the game only gives a subtle hint at first while you accidentally put too many charms, making it so that only an attentive and/or persistent player will keep on sticking the charm until the notches break. So small yet so crazy to discover.