Surefire X300 or Streamlight TLR-1 HL. The Streamlight will give you 200 more lumens for about half the price of the X300, but the durability of the X300 is unmatched. There's also the new Surefire XH35 which has 1k lumens and is priced equal to the X300, but I'm not sure if there are holsters for it outside of the Masterfire line of holsters it was made for.

ETA: If you like watching video reviews, I believe Aaron Cowan of Sage Dynamics has reviews of all three of the above mentioned lights on his YouTube channel.