An Ammunition box (or an "ammo can") is a popular choice for a long lasting cache container. They are considered the gold standard of containers because they are very sturdy, waterproof, animal and fire resistant, relatively cheap, and have plenty of room for swag.
It's very important to label ammo cans clearly so as to avoid any unnecessary unpleasantness. Mark cans with words like:
- resold empty
- Game Piece
Also include a cache-site web address on the outside.