Give back, rude

Sell, gauche (with some exceptions for real estate and timed items like concert tickets)

Give to someone else, depends:

Is it a family heirloom? Must be given within the family.

Was it handmade? Must be given to someone else with a connection to the maker.

Is it something that if taken care of can last for generations? Must be given to someone who will be a good steward of it.

For most other things, regifting is fine, including entering it into a mutual aid resource pool.

One more note: If the gift is replaced by a nicer or updated gift from the same or related source (eg. your parents get you a new laptop, replacing one they gave you five years ago) then the older one is free for you to do as you like with.