WD40 can be used as an external Metal Preservative, as it evaporates and leaves a parafin wax coating that will protect against rust. However, it should NEVER be used as a Gun Lubricant as that parafin mixes with powder residue to form gunk and WILL clog up the action of your gun.
Ed's Red Formula is very good as a bore solvent and general solvent. Very good for removing carbon, but only so so on lead and copper. Trouble is, as a Solvent it should only be considered a light oil. Protection of bearing surfaces will not be as well done. PB Blaster Penetrating Oil is sort of a Commercial version of Ed's Red.
Baby Oil is basicly thinned Mineral Oil, which is very slippery stuff. Hoppes Gun Oil is nothing more than regular Mineral Oil that you can buy rather cheaply in most any Department Store. Relatively Non-Toxic, too!
I like the straight 30w Motor Oil and Mobil 1 Full Synthetic 10w30 for a number of reasons. Have used Straight 30w on a number of commercial/industrial machines and on my Dillon 650 Reloading Press. (Dillon Specifies it's use!) Also, a few top IPSC shooters used it as their lube of choice to keep their high dollar race guns, running! One used it to keep his pistol going some 200,000 to 300,000 rounds. (There were the expected replacement of minor parts and two barrels.) Mobil 1 Full Synthetic or most any Full Synthetic Motor Oil works very well in harsh climatic conditions and I use it in my AR15A2's Bolt Carrier, as I consider that area of the gun to be a harsh environment, as the gas comes directly in there.
There are a lot of choices and options when it comes to lubing your gun, and many will work very well!