The two biggest names in weapon lights are Streamlight and Surefire.
For Streamlight your best bet is the new TLR-7
TLR-7/8 Series
Surefire has their XC1-B light
WeaponLights | SureFire
In general Surefire is considered absolute top of the line war fighting gear, and you pay for it. Streamlight delivers 95% of the performance at half the price.
Yes there are other options, such as Olight, but everyone I know who bets their life on their equipment choices Surefire or Streamlight.