LotR sayings can fit any where!

[dancing spawn of ungoliant]

Has anyone used, "Aiya Elenion Ancalima!" when using a flashlight?

No but if I see a nasty spider, I shout "Aiya Eärendil Elenion Ancalima" and drop a heavy book on it. Yeah, not so courteous but I'm afraid of those eight-legged creatures.

Another my all-time favourite is very useful when dealing with kids. "Show them no mercy for you shall receive none!"
Then there's of course "Who enters my domain?" when someone enters my room.