When I was first putting together my GHB and BOB, I tore my house apart looking for some good flash lights. When I came up short, I realized I had a couple of LED lights in my bag of Diving Gear. That's when I remembered I had two Princeton Tec Blasts that were perfect additions to my preps.
Over my years of diving I've bought several different models of Princeton Tec lights, from cheaper to more expensive. Every light I've used has been well made, bright, and about half the price of most dive lights. Specifically, I've had two of these small Blast lights for over two years as back ups when diving. They've been abused, taken diving, loaned out to friends, dumped in the dive bag, never really maintained (unlike my more expensive dive lights), and yet they worked perfectly (still on the original batteries too) and looked almost brand new when I just pulled them out.
They're designed for use in salt water, one of the most corrosive environments available, and heavy pressure environments so they are incredibly durable.
For the quality and the price, these little lights are hard to beat. You could toss them in a GHB or BOB, forget about them, and you can be confident that they'll work when you need them. Definitely a good addition for the price.