Last spring, Samm Sheperd created this amazing overclocked, water-cooled LED flashlight that pumps out 72,000 lumens, using about $700 worth of parts.
(He recommends that people who want a similar vehicle-mounted effect go for an off-the-shelf light-bar)
I used to live in a flat on the fourth floor of a building on a quiet street near a lot of London nightclubs, and at night, we'd get insanely loud drunks staggering down the road, the sound echoing into all our bedrooms. I bought a "drunkard-startling torch" — a huge flashlight — that I'd use to get their attention without adding to the shouting, then ask them to keep it down. About 80% of the time, this was all they needed; the other 20% of the time, it would provoke obscene shouting.
My drunkard-startling lamp was also good tonic against the opsec-challenged drug-dealer who'd park his boom-car under our window at 3AM and wait for his subcontractors to bring him the night's take; a high-lumen reminder that he was advertising his presence to people who could narc him out with impunity usually sufficed to get him to turn down his stupid autotuned shitty generic house music.
All to say, giant honking lights are pretty useful!