Hey Matt,

Optimal solution would probably be an HDS EDC light, but a Glo-Toob FX might be worth considering.

While not multi-function, the Gerber Infinity Ultra would be a good thing to have on hand. Very rugged, esp. if you can find the old design, or the Ultra-G version. All versions are quite waterproof. I tend to keep these around with lithium batteries as a backup.

The Arc AAA also falls into this catagory. With a lithum cell they make a great backup light.

Boating, I think I'd consider having a UK 2L on hand, maybe with the eLED module. The UK 2L is very rugged and very waterproof.

-john