I've used both WD-40, Boeshield T-9
, and Corrosion-X
depending upon how much residual film I felt was needed.
Ballistol is a product I've been reading about from a website that I purchase off-road gear from sometimes - read down to the steel wool-in-water test - it's pretty interesting stuff, but I've not ordered...yet.
I've also started using Motorex Joker440 in cases where I'd used WD-40, it's a synthetic based spray lube. This youtube video
isn't something I'd condone but is pretty convincing that it does not conduct electricity and is pretty waterproof