"WML" is the term of art. Weapon Mounted Light.
Surefire X300U-A is the go to. Have several. Even use them on carbines.
Streamlight is right behind them, a little less sturdy generally. I have one on a carbine for reasons, and the TLR-6 on my pocket pistol as I prefer the form factor, it's already so small and plastic it should be fine. I also strongly prefer the SF switchology (rotate AND push both work). And me, I LOVE the DG switches. Strap runs back to sit under your middle finger, light turns on when gripped. Some disagree with it for safety reasons, I have a non-trivial human factors background and don't buy those arguments.
Surefire and Streamlight will be the ones that holster makers who build for lights work with as they are duty grade. Others, not so much. To the point that someone makes cases for O-Lights that emulate the footprint of an X300.
From some experience, lots of the other brands are not really up to the task, so if you carry while hunting or whatever, outside, in rain, bang it around: spend the extra on the Surefire or Streamlight. If at home only, pretty much whatever.
Also have a handheld light. Never use the WML for searching, etc.
Next, we'll get you into a red dot on your pistol!