Electric arrows do more damage in the rain.
If you get a headshot on an electric Lizalfos, it does an electric bubble, electrocuting everything around it.
Cooking just 1 hearty radish does a full heal and 3 bonus hearts. (this is good food for the Ganon fight)
There is a Hylian woman in Rito village who pays a ton for Baked Apples, and even more for ones in bulk. (it's very easy to warp to death mountain and cook them on the ground)
The Cryonis Rune also works on mud and tar.
The Master Sword glows and does 60 attack when fighting guardians (as well as in Hyrule Castle) and lasts a lot longer.
If you unequip your items (bow, sword and shield) you make a lot less noise.
If you use octorock balloons, you can make rafts fly.
Some weapons respawn, like Royal Guard's gear and near the Gerudo tower there is a respawning Edge of Duality. (50 attack claymore)
If you light 4 or more campfires it causes an updraft and NPCs run away or cower in fear.