I use an Inforce on my M4 (INF-WML-B-W-M-H).
Lightweight, 200 lumen, momentary on switch only and uses 123A battery.
Can be had for about $120.
This. I run Inforce "momentary only" WMLs on several of my ARs, from my 16" recce to my 9" SBR.
As was stated, they're nice and compact and not weighty. The WMLs have an integrated attachment piece for the rails. They work especially well w/ Hailey Strategic's Thorntail offset mount.
And unless you're conducting searches out in the fields or boonies for escaped convicts or ISIS-invaders, you don't really need to be hanging a heavy, hi-beam type on your basic home-defense AR, ... and certainly not on a multi-purpose grab-n-go carbine.