Ooh, Ooh, Ooh! I use my modified version of Ed's Red + Kroil. Seriously though I got suckered into buying a small bottle of Lucas Extreme Duty Gun Oil because it had a cool needle applicator. Seems kinda thick which I like as my Ed's Red which is mostly for cleaning is pretty thin. I have so many varieties of Gun Lubes downstairs its not funny.
Some of the more modern lubes seem to be closer to waxes and can get sticky if applied too heavily, allowed to sit for extended periods or used in cold weather. For an AR-15 that I can run a bunch and get hot they work pretty well on the BCG but I tend to stay with thinner lubes for my pistols.