For me the best light is the one that is in your pocket when you need one. I carry this little , cheap, bright diver's light on me.
I just put a cheap , but adequate Boker light on the botton of my Ak, via a tri-rail
& I will be getting this one next month for my 870.
Streamlight® ProTac™ HL C4® LED Tactical Flashlight | Bass Pro Shops
As far as 123 batteries, I use a lot of them, I get the red colored , Surefire's from Lowes, they are $5.00 for 2 & last a while.