XLR-250 Kill Light, fantastic value, amazing quality in a light.
Bipod vs light? Get the light. A simple set of x shooting sticks will be as effective as a bipod, but a quality light is hard to beat. A great option for a light system, rather than gun mounted, is one mounted on your mono-pod or shooting sticks. It drops the level of the light beam so it's not directly in front of your face, helps prevent glare blindness.
For a heavier wallet, the subzero lasers are fantastic, but for the price, I'm hard pressed to say they are worth it. Primos lights and cabelas lights are decent, but I'd go with the xlr-250 hands down.