The stocking stuffer trap is buying something pickleball-themed instead of something pickleball-useful. Socks with paddles printed on them are themed. Here is useful.
š The list
1. A Dink Ink ball stamper ($15). The one gift on this list they will use every single game for years. Their initial or their personality (a dinosaur, a shamrock, a coffee cup) inked onto every ball they own, so the whose-ball-is-this ritual dies at their courts. Pick from all 56 designs, and if you do not know their vibe, their first initial never misses.

2. Fresh overgrips. Every player's grip is worse than they think. A pack of overgrips is the cheapest performance upgrade in the sport.
3. A tube of balls. Nobody has ever been sad to receive pickleballs. Bonus move: stamp them with their new Dink Ink before wrapping, and hand them the world's first pre-personalized tube.
4. A sweat towel or wristbands. Unglamorous, constantly used, always forgotten at home.
5. Court snacks and electrolytes. The between-games currency of every rec group.
Useful gifts get used.

The stocking math
A stamper, a pack of grips, a tube of balls, and a towel lands around $40 total, fills the stocking, and covers everything a player burns through in a season. If you only pick one, pick the stamper: it is the only one on the list that is personal.
Shopping for a bigger gift to put under the tree instead? A beginner in the family gets more from a $36 doorway trainer than from any paddle upgrade, and the full kid version of this list is here.
FAQ
What is a good pickleball stocking stuffer?
Small and useful beats themed: a personalized ball stamper, overgrips, balls, and a sweat towel. All $15 or less each.
What pickleball gift is $15 or less?
A Dink Ink ball stamper at $15: their initial or a fun design, self-inking, reusable on every ball they will ever own.
What do pickleball players actually want as gifts?
Things they run out of (grips, balls) and things that are personal (their own mark). The combination covers both.
What if they already have every gadget?
Personalization is the one thing they cannot already own. A stamper with their initial makes gear they already have feel new.