Spendy, but nice addition - SureFire X300 Tactical Handgun / Long Gun LED Weaponlight w/ Universal Mount, 170 Lumens

Fits on snug, but not so much that you can't remove it. Activation switch for "constant on" works up or down, which is nice. That way the device conforms to your style, not forcing you to learn to activate it in an odd or uncomfortable way. Also pushing with the trigger finger (or any other, I suppose) you can temporarily activate light. This is also a nice feature. It seems like a lot of thought went into this device. Although expensive, it is a wonderful accessory. I'm very glad I purchased it.
Pros: light weight
Cons: low holster choices

This review was written in the old system and had content requirements that are different than reviews written today.