Hasn't been a lube thread in a while so...
Ever since I started collecting flashlights I had been using Gun oil for lubricating threads. For the most part it seemed to worked. It minimized squeaking, but it was a little messy.
On a whim I went searching for a better solution. I saw Super Lube recommended several times (had to dig for thread lube recommendations in general). $5 for a fairly large tube? I'll give it a shot.
http://www.amazon.com/Super-Lube-21030-Synthetic-Grease/dp/B000XBH9HI
So I did and I don't think I've made a better $5 purchase ever. It smooths and silences all but the absolute worst threads (still vastly minimizes the worst threads). It corrects or improves on sloppy/loose threads. It covers quite well (I've cleaned and lübed up bezel threads and front and rear battery tube threads on every flashlight I own [around 75] and still have about half a tube left and I tend to use ample amounts.)
It doesn't seem like it would change much, but it really does.