Well, Zelda: BotW is full of little details. A lot of people probably already know about these though.
1: You don't need to catch fish. Just throw a bomb in the water and the fish will die and drift to the surface for you to pick up. (electric arrows work too.)
2: Holding a fiery weapon actually produces heat. Which helps with melting ice, keeping warm, putting things on fire, etc.
2.5: Fiery weapons also produce steam in the rain.
3: The shade is actually cooler than being out in the open.
4: Lighting stuff on fire (like the grass) creates an updraft for your glider.
5: If you throw a boomerang at a Lizalfos, which is their preferred weapon, they'll simply catch it.
6: Enemies don't just go for their own weapons. They go for any weapons they can find nearby. (better not drop your best sword near them)
7: Some monsters will get distracted by food on the ground, rushing towards it to eat it.
8: Shooting a metal box with an electric arrow creates a damaging electricity field.
9: Metal weapons start sparking during a thunderstorm, indicating you'll get hit by lightning soon. Throw it at an enemy and it will get hit instead.
10: Bomb arrows don't work in the rain.
11: Rolling a small snowball down a hill will make it pick up more snow and become bigger.
12: NPCs can have custom dialogue depending on what you are (or aren't) wearing.
13: Using stasis on enemies and moving out of their field of view surprises them.
14: Your horse will 'steal' things like apples from offerings when you're not riding it.
15: Some puzzles involve metal boxes to complete an electric circuit. Your metal weapons will work too.
16: There are different climbing animations depending on how steep the surface is, and how much stamina it costs.
And these are just a few examples.