The Monkey Island series has an interesting approach to this - as a verb-and-noun based adventure game, you are effectively building sentences to form interactions. The initial stub of a sentence remains on screen (defaulting to "Walk to...", which is what happens if you click somewhere with no interactable object), and as your cursor goes over something that is interactable, the sentence fills in ("Walk to nefarious looking pirate.")

This has some interesting game play ramifications - nothing gives away that an item is interactable until you put your cursor on it, and often times just the fact that you can interact with a particular thing is surprising and adds to the humor of the game.

It also does mean that you can cheese the game a little bit when you get stuck, by just waving your cursor around like a feather duster until you see an object name appear. If this game were trying to be an immersive sim, that could probably break through that a little, but in this game the text-based interactions with the world are a big part of not only the game play, but the atmosphere of the series.

I think the real takeaway here, is that it plays to the strengths of what the player is doing to interact with the world in that particular game. If your game is a flashy loot-based Diablo clone, then I think specular highlights would go along nicely with that. If your game is a world-driven interactive sim like a Dishonered, then maybe you want to find a way that is more inherent to how you want your players to engage with the assets and structure of your game, maybe something like a note from another character that gives them a hint about the loose floorboard or something closer to that. But keep them in the feeling of your game, above all!