My "go to" protectant is often white lithium grease. It seems to do a good job while lasting the longest if the things I've tried so far.
I use it in locks, clips, chains, cinch pins, utility cart axel and hitch, various spots on the ATV. If it's got metal, I most likely use this stuff on it. Well, not my fencing. That would be a daunting task to grease over a mile (or more) of fence.
I tend to avoid the aerosol grease, preferring the type in a can or squeeze tube. Maybe it's just my own preferences, but I don't think that the aerosol works as well.