The Nite-ize LED light WS sells is awesome!
It is not a flashlight (though it dies have a flashing option). But for simple use as a hammock light it is perfect. It is an orb shape with a rubber exterior so it will not catch on anything. It is also a diffused light so it diffuses light around the whole hammock interior. It has a sturdy wire gate so it fits perfectly on your ridge line. If you wanted to go all out you could buy a set of 2 if you have a diamond tarp and put them on your guylines to keep others from tripping on them in the night.
Perfect kit, low price. Pick one up with your regular order! I think they're $5.90.