Most satisfying gaming mechanics
1. Enemies that appear on the world map. As in not random encounters.
I hate being forced to fight a random enemy every few steps. What if I had the choice to fight enemies every few steps or running right past them? That way I can level when I want to, or not level. The choice is up to me. Also I have the option to grind a particular type of enemy if I need to.
2. The alchemy system in
Secret of Evermore
I'll explain this as I've not seen it used anywhere else. I'm sure it's not the only game to use this systme but it works so very well.
In this game you cast spells but you have no mana or any mana like resource. The resource you need to cast spells is alchemy ingredients. You either find them in the world (limited quantities) or you buy them from vendors (only limited by how many you can afford at the time). Sure this game is not balanced at all. But if it was, it would make gold/money a valuable resource and it'd really make you think when you use your spells in battle. Also in this game spells are levelled up by using them over and over. That's lots of trips to the vendor for ingredients so lots of gold farming. early on do you want to spend your gold on armour or on more materials for more powerful spells? Sure the spells get way too powerful in this game but in a properly balanced game this would work really well.
3. Switch gyro aiming.
It's so much better than aiming with the right stick. Honestly any Switch game that is shooty shooty bang bang that does not offer gyro aiming as an option is doing it wrong. Sure not everyone likes it, that's why it should be an option.
4. Movement in turn based combat games.
Dragon Quest XI is a recent example of this. In the 3D battles you can move all over the little battle area. Does it affect the actual comat in any way? No. However it makes the combat more immersive and less like boing text based turns. At it's core DQXI is just a text based adventure with a lot of graphics added on top. This text based core (which existed in every DQ game since DQ1 which itself was based on actual earlier text based adventure gameas) is still there, it's just more in the background now and most players won't even notice it.