Some guns, seem to “like” to run “wetter” than others. But even modern, polymer frame need some lubrication. And any wheel-gun can benefit from a drop or two of good quality gun oil from time to time.
Serious “operators” who go in harm’s way agree that while many of the guns today can function in less-than-perfect conditions, none of them would ever carry a dirty gun on purpose. A defensive handgun should always be clean and properly lubricated.
So, what is “properly” lubricated? If you have just come back from a trip to the range, once you have unloaded your gun and done your basic cleaning, just a bit of lubrication on the key parts will likely be more than sufficient.
Starting with a revolver, the “key parts” will be the point at which the cylinder rotates around the ejector rod, the cylinder ratchet area, and the trigger group. In some guns, the ejector rod rotates along with the cylinder (Smiths), while in others the rod is stationary (Rugers). Point the gun up to let the oil penetrate. Then, point it down at about a 45 degree angle and spin the cylinder. It should spin freely for several seconds. If it stops after only a revolution or two, some additional cleaning and/or further investigation may be necessary.
The trigger group is best handled by turning the revolver upside down and placing a few drops of light oil on either side of the trigger where it meets the frame. Wait a minute or two to let it work its way into the mechanism, then turn it over and add a drop to the base of the hammer. Then, dry-fire the gun several times to be sure it works smoothly.
Semi-Auto's should have light oil sparingly applied to the trigger and firing mechanism (something like Rem-Oil spray is excellent). Then apply oil to the slide rails. A few drops at the back of the slide is usually sufficient, and on the frame where applicable.
The barrel should have a thin film of lubrication, including on the area of the barrel that locks into the slide. Since a carry gun stays close to the body (at least it should), it stays quite warm even in winter, so an alternative to oil is a quality grease (Rig +P). Unlike oil, it will not evaporate or run out. But apply ONLY to the barrel and slide rails.
Other options are Militec-1 and Frog Lube. These are “metal conditioners” which “bond” to metal under heat, and retain lubricity even when dry.
Remember to train regularly and clean your firearm.