So many, I like when you get a lot of levels and upgrades, but each one does barely anything, but you get a fucktonne of them, and see how all these tiny changes to your character adds up over the course of the game to you being overpowered AF.
I like the idea of having multiple effects attached to your very basic actions, which modify them in small but significant ways, progress must be small but measurable and predictable, and must come through adding a singular effect, not multiple effects at once, unless its a trade off that improves one thing at the cost of worsening another thing, but in those cases it would be nice if later on there's something that can undo the cost side of the trade.
I thought vampire survivors was cool because it felt like I was a boss in a danmaku game, just spamming attacks all around me in a pattern or according to some rule rather than directly aiming at my opponent.
I also thought that unicorn overlord was neat as well since the jrpg was changed by giving the party a set of rules on what move to use and when, by passing all those hours of manually selecting actions during combat, yet not removing the gameplay of the jrpg and instead redirecting that to optimization.