What are some activity examples that train finger or hand dexterity?
When thinking about character features in video games, dexterity is generally about doing something swiftly or dodging stuff.
I assume you mean IRL activities?
Also repairing clothing with thread and a needle
For Ambidexterity, brush your teeth with your non dominant hand.
I either cut my gums, my cheek, or both.
... with a toothbrush?
You know you're not supposed to use steel wool as a toothbrush?
Physically how?
Guitar and magic tricks.
Ideally both at the same time.
Jason Becker used to shred left-handed while yoyo-ing with his right hand
https://m.youtube.com/watch?v=2QOFPADkTlw&pp=ygURSmFzb24gQmVja2VyIHlveW8%3D
Guitar, piano.
That knife game where you stab the table between your fingers as fast as you can.
Playing a piano can do this because the velocity of each keypress is a big part of the expression, and it’s a scalar value meaning infinite degrees of possible variation.
Definitely piano but most instruments work. Maybe guitar a bit more but not with a pick.
Piano playing and touch typing come to mind
Air guitar
Have a look at pen spinning
Video games can get pretty finicky when you go off the beaten path, requiring a lot of extra "mechanical skill" to get right.
A certain glitch on a game I play involves carefully timed button presses while keeping the control stick in a specific, narrow range just outside the "deadzone". You then go fast, and backwards, and have to steer by switching which side you're holding the control stick on. If at any point you go out of that range (either through the center/deadzone or tilted too far), it instantly stops working. And some other tricks in that game are hard.
So that sounds like a good way to practice some dexterity, I know it's helped mine.
Other than that there's stuff like Rubik's cubes, arts and crafts,
Wavedashing / wavedancing?
Ocarina of Time, "Hyper-Extended Super Slide". Roll into e.g. an explosion, shield and target on the same frame within a certain frame window. For reasons, you go fast, and can retain the speed by keeping the stick in "ESS position".
I wonder if the new Street Fighter would be good for that, since it's put a lot of effort in to teaching new players.
Boxing