The magnetic ring (infinite variable output) is one of my favorite options for one simple reason, you can have exactly the "mode" you want, everytime. Nitecore's implementation is not as good as sunwayman's but, it is ok-ish.
By the way, it is a 1x18650 (or 2xCR123A), 345 lumens and was less than $70 on DD.
...but if I had to pick one, P60 for sure.
Like some of the others had mentioned...it's small enough to fit in your pocket (unless you like wearing skinny jeans, lol), it puts out good amount of light for it's size.
Currently my favorite is the solarforce meat tenderizer (sorry forgot the actual model name). It not only functions as a torch but a hand massager/warmer.
My most indispensable light isn’t a 18650 but the most indispensable 18650 I have would be a general P60 with XP-G diffused (3 modes no strobe) and a forward clickie.
I’m sure I’d rather have the SC600 however.
I gave away my C8, fail to see what the hype is about, perhaps just a poor version, can't even remember where it was from.
I'd vote UF 980L, amazed no one has mentioned it until now!
You just got
one of the very for a very low price!
You know the Best 
I wish had sean that 5 days ago!
But you Rock friend!