I spent several hours last year researching flashlights.
Basically, my goal was to find the smallest flashlight I could with the highest lumen output and that lasted the longest and also either had a single output mode or memory. I hate having to click several times toget the brightness I want each time and also clicking several times to turn it off
I use a Fenix flashlight model PD32. It has 5, 50, 150, 400 and 900 lumen output.
The beauty of this flashlight besides being very small and lightweight is that it will run 400 lumens for 4 hours and 900 lumens for 1.55 hours. It uses 1 18650 battery which is nice because they only take a second to swap out. The other awesome feature of this light is that there is a tail push switch which you can either click on or just hold for brief illumination. Lastly, there is a secondary brightness button on the side of the flashlight to flip through brightness settings and the flashlight will stay on whatever setting you have it on whenever you turn the light on and off without having to cycle through each time.
Here is the link to the official website, although you can purchase it on Amazon as well.
PD32 Fenix Flashlight - 2016 Upgrade - Fenix Flashlights