I've used a ton of different stuff. FP-10, Slip 2000 EWL, Break Free, MPro 7, Lucas Gun Oil, Hoppes Oil, ATF, Mobil 1, various greases like Lucas Red N' Tacky, Redline CV-2, and Super Lube, Triflow... even some engine assembly lubes like Torco, Comp Cams, and Lucas. Still waiting to try Weapon Shield but I have enough lubricants. I have a lot of greases because I used to do a lot of work on cars and motorcycles, so I just used what I had on hand.
My favorites thus far have been the Slip 2000 EWL for oil and Super Lube for grease. Engine oil is great but doesn't offer much in the way of corrosion resistance. It also tends to stink when firing. Engine assembly lube is great too, but tends to be thick. I like to cut it with a lighter oil 50/50. But the Slip 2000 EWL I can easily carry in my range bag and it works great. It even freed up a sticky action on my friend's Beretta shotgun after he let it sit for a while with Break Free in the action.