It seems like RIG (Rust Inhibiting Grease) gets top spot for persistence and durability in all the surveys I have seen.
I myself, ignoring what the latest polls/tests show, use something synthetic and on hand, like Brownell's Action Lube, or disc brake caliper grease on the rails and other sliding parts. I also use Breakfree CLP on the other areas.
For my range guns, I tend to keep them "wet", and also clean them often. For my carry guns I use grease rather sparingly and don't overdo it on the oil application.
For what it's worth, using Brownell's Action Lube can get costly over time, so take P95Carry's advice and just find something with moly or teflon and go from there.