Surefire 6P with Malkoff drop in is on my primary AR15.
Surefire G2X Tactical is on another 'go to' AR15.
I have parts on order to put together a Surefire 3P clone to use on the AR's. The dedicated weaponlights on the market are nice but don't seem worth the money for me. Both of my current Surefires were aquired at really good prices, so I'm very happy with them...especially the 6P. But, I'm looking to go to a single cell lighter weight setup without spending hundreds, so I'm looking forward to building the 3P clone.