First, the obvious
Keep some emergency cash in it.
Buy some gold and/or silver rounds to keep in there for when the economy collapses.
A safe helps you keep what you have, in case of burglary or even dishonest people attending events in your home.
Now for the less realized
Owning a safe attracts money. What? How?
On a psychological level, a safe is “gravity” for valuables. Knowing you have a safe place to keep valuables can help you want to accumulate those valuables. Also, the amount of empty space in a safe can inspire a sort of “game” to fill it with valuable items.
A good starter safe: https://smile.amazon.com/BOFON-Fingerprint-Password-Safety-Security/dp/B09XMRSSZH