I own a SureFire E1B, about a $160 light. But in a situation where I don't consider the light to be life and death and very well may get lost, I have a bunch of powerful yet cheap Chinese lights that I'll take. They cost between $7 and $16, and losing one won't sting quite as much.

Of course the danger is valuing a piece of gear over your own life! No matter how expensive it's still just a thing. If it's too expensive to use it's probably too expensive to own.
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“I'd rather have questions that cannot be answered than answers that can't be questioned.” —Richard Feynman