A weapon-light is one area where you shouldn't cut corners because if you need it and don't have it, you are fucked.
I will not recommend anyone but Surefire, they are solid built and have an awesome customer service department if you ever need them. And chances are, you will never need to talk to them again after your initial purchase. If you intentionally/unintentionally do something stupid to damage your light (like drop it out of a backpack while riding a motorcycle with it attached to a loaded G17- don't laugh, granted the light still works 100%) they will bend over backwards to fix it for you.
Go ahead and pony up for a Scout, Mini-Scout, X300 or a Scout/Millennium with a V2 head. Yeah, you may spend $300 on it, but you won't be back in here or the light/laser section in a few months when your Streamlight/other Surefire-Knockoff shits the bed on you.
I see this trend in the SF to shy away from spending money on good weaponlights/optics and instead spending 10x the initial cost stocking up 10s of thousands of rounds of ammunition. Have a quality weapon, quality parts on your gun, and a few hundred rounds ready to go. You won't be getting into any 1000rd firefights, but you might be in a situation where you will need to illuminate something after beating your rifle to hell. You want to make damn sure that your shit works when you need it.