What are some creative ways to use an unused telephone jack outlet?

That room could be rented for $1k a month in California
On it, I’ve got a 3d printer ha

Test your drywall repair skill.

Already solid <3

Is it still hooked up? You can draw some power from the line and hook up some low power leds, or maybe run a trickle charger for rechargeable batteries. If it's disconnected, it would make a decent hidden vault with a cat-shaped key.

You could also plug in an old phone and get a landline.

It’s still hooked up but idk what I would display with the leds. It’s basically circuit breaker to phone line.
Maybe I should swap my cell for a vonage plan

Little CAT3 powered xmas tree

Get some dialup and see what is on alt. nowadays?

Hide your ricin.

Wouldn't put more than like 5V DC on it, but you could use it to put power to some low power USB toys.

Remove the faceplate for the outlet
Install electric pencil sharpener
Reattach faceplate

Weed stash.

Assuming the wiring is still in place but no longer hooked up to the phone network, there are things you could do with that:

I could be mistaken, but I think I remember (from back in the day when it was more common) their being ways to use phone wiring to network computers, or send a signal from an amp to speakers in room (I have some doubts about the latter, since speaker wire normally a lot heavier than phone wire).

Doorbell or intercom is another thing that you could use it to connect between rooms. You could even rig up old phones between rooms (without being on the phone network), though you'd need to supply power and maybe jury rig a button to ring them across the line.

If you had use for some other kind of wiring, the wires could possibly be handy for pulling the new wires through the wall.

though you’d need to supply power
Go for really old ones with the crank handle for ringing. Like from army surplus and you don't need the power :-)
We played around with these for a day in the army https://en.wikipedia.org/wiki/Feldtelefon_50 when you crank the handle while your friend is still putting down the line you can shock them.
Pulling wires would be the best thing. Ethernet where it is is great. The issue is that the wire is clipped all the way through. You can’t just pull