The Streamlight ProTac 2L-X is an incredibly versatile tactical flashlight. Sure, other flashlights might have better beams, higher lumen output or higher grade materials, but the Streamlight ProTac 2L-X is the best combination of the above factors.
Don't kid yourself into thinking that the ProTac 2L-X doesn't have the power or durability you need in a flashlight. The light itself comes with a high IPX7 waterproof rating (1 meter depth for 30 minutes) durability rating with a strike bezel.
Another helpful feature is the ability to use either a single rechargeable Streamlight lithion-ion cell battery, or two CR123A batteries. The rechargeable batteries will last 3 hours and 15 minutes of constant runtime with 500 lumens, and running the flashlight on low (40 lumens) will give you 30 hours of battery life. The two CR123A batteries don't perform quite as well, lasting 2 hours and 45 minutes on high and still 30 hours on low, respectively.
The housing of the flashlight is aluminum coated with Type II Military Spec anodizing that adds to the durabily of the light. The head of the light has anti-roll shaping so it won't roll away from you on a flat surface, complete with a removable pocket clip and carrying case.