1) How about some kind of graphic that appears a couple of pixels above an enemy's head when you throw the boomerand at it? It could be like stars spinning round or something like in the Minish Cap.
2) Make it so that secrets can change what string is used on a certain screen. This could go well with a side quest that requires you to do something on another screen to get someone to say something different and important on another screen so you can progress. Like when you cannot speak Minish in the Minish Cap but then after you learn what the Minish people say is a different string written in English so you can understand it.