Here’s a really fast one, as Dragonflight brought a very helpful tool with it that helps fight, well, bugs in object placement, basically.
As spotted by think_brainblast, the interact key can actually be used to get at objects that are stuck in the scenery and are difficult or even impossible to get to, like ore or treasures. Keep in mind that the key orients itself based on camera position, not character position.
The other very useful function we’ve already covered is for fishing, as you can use the interact key to do it entirely without a mouse! And, of course, there’s the basic and intended use for the key, as it lets you interact with quest givers, NPCs… well, everything really. Definitely give it a try if you haven’t, as it’s one of the most useful things added to WoW in quite a while.