Hoppes Elite,Frog Lube, Go Juice, Break Free, rem oil, syn motor oil mixed with ATF fluid, depends on the gun, etc. I like frog lube for rust protection and it has no chemical or petro smell. Go Juice has no smell to me and is good for autos.
I hear the special formula WD 40 Rust Protection spray gel is good for gun rust prevention. You can get it at Walmart. It works well on hand tools. Regular WD 40 is barely better than nothing.
I used 3- in- one oil for decades and it did fine so long as I did my part. It is way down on the list so far as gun oils go. Hornady one shot is rated very high, but I've never found it in stock when I was buying oil at a cabelas, etc.
If you can find them there are several good lubes now designed for guns. Many more than the old 3 in one days.
I'm picky about gun lubes, so I use several different types for different purposes. These are what I've found to work best for specific puposes.
-Break-Free CLP is kind of the "if it doesn't need something special, use it" oil; and it's pretty good at preventing rust. Most rimfires get CLP.
-Eezox for exterior rust protection and interior bore protection (dry patch before shooting).
-Tetra gun oil for 1911s.
-Slip 2000 EWL for AR/M4 bolts and carriers.
-Glocks and XDs get a combo of CLP on some parts with TW25B grease on the slide rails.
-Pro-Shot Pro Gold grease on bolt action locking lugs.
M-PRO 7 for my shotguns. I apply to all moving surfaces then wipe off all excess. Only lube I have found that doesn't cause slow cycle or no cycle in extreem cold temps. It really sucks arss when your scatter gun slow cycles or doesn’t cycle fully when when you have a group of birds trying to get out of the hole after the first shot.