You want one that has good fire proofing and can withstand the heat for a long period of time. I have a Liberty "Freedom" series. It was priced right and does the job.
It holds 15 long guns and has 4 shelves for other items. The electronic lock will add to the cost. The dial works just fine. I do not have a humidifier and have no corrosion issues. Just don't ever put a wet gun in there! I bought a strip light form Home Depot for $10 and used double sided tape to hold it out of the way.