Just picked up a Fenix pd35
What an incredible light that is. I have been a flashlight fanatic for 20 years, and the PD35 still impresses me. I run 18650s in mine, as well as several other lights like the also awesome Fenix TK22. Just ordered a PD32 today for giggles, along with 2x 18650, another charger, light cone and diffuser.
I think the 18650s are great. At 2600 maH (give or take), they pack a lot of runtime even at high output. I think they are great. Just get a quality protected brand like AW, Fenix, etc. I've been running AW's for years with good success. Rock on.