Wario Ware games, Ring Fit or any game implementing Gyro controls has made good use of the controllers capabilities.

Super Mario Odyssey, although optional was truly in part due to the use of motion control to do different kind of Cappy throws on the fly

Mostly Gyro-aiming, like I did on the Wii U already.

Okami was the game that got the best out of the Joy-Cons in my opinion, as silly as it sounds. Gyro aiming worked great and it was the only game where I even noticed (and enjoyed) the "HD Rumble".

gyro aiming

I'd really like to see new games employ the Joycons for sword combat like Red Steel 2, Skyward Sword, and Wii Sports Resort did on Wii.
Gyro's awesome, but the motion functionality on Switch feels a bit under-utilized outside of party games.

I think that kind of motion control seems more at home in VR. Especially a game like Red Steel 2, which would be awesome as a VR game.

That said, Switch Sports has Chambara, if you're into that.

And I wouldn't say motion controls on Switch are underutilized per-sae, since I gave plenty of examples outside Gyro aiming. I think it's more that developers have learned that they don't have to shove them into every game they can like they did on the Wii. A lot of people didn't like they early Wii era of constant waggle to replace a button press, due to the controller's lack of buttons.

The Joy-Con have a full controller layout, so developers don't have to use motion controls if they don't want to, and most developers implement them only if they actually have an idea for them. It's like the DS where it has a touch screen, but games didn't have to use it if they didn't want to.

I don't think I really played much where you use motion control. Maybe indeed aiming in Zelda or something so I guess that's my favourite use.

Some other examples I enjoyed:

- Touching the Joycon camera to the other Joycon/hand to reload in the RE Revelations Collection, as if you were inserting a clip into a gun. Was one of those little things that was just really nifty.

- Slicing baddies in half in No More Heroes 3. Insanely satisfying.

- The motion option in Nier Automata. Attacking by shaking the right Joycon and dodging with the left was nice and simple and felt good.

Skyward Sword HD and Metroid Prime Remastered for me. I was shocked how close Prime came to replicating the feeling of the IR pointer in the Prime Trilogy, even if it did need to be recalibrated more. And I always loved the motion controls of Skyward Sword. I didn't notice any real improvement over the original Wii version, but I didn't need to.

IR aiming for Wii is more precise than the gyro on switch. So, it makes it easy to say aiming is a bit of a downgrade when it comes to accuracy.

I have enjoyed Switch Sports, Ring Fit Adventures and Fitness Boxing but you do need to be in the right mood/setting to play those.