Flying with wings strapped to your arms! Not outside on the moon of course, but could maybe work in a cave or building pumped full of air. I remember reading about that in some scifi novel long ago.

Randall Munroe did a what-if entry about swimming pools on the moon, and swim-jumping would be wild. If you have fins, you could do dolphin jumps several meters above the water!

One of my probably-not-safe-enough ideas was to combine underwater rugby with above water rugby, and perhaps even aerial rugby! A couple of strategically placed moderately sized fans in an indoor sports hall, where part of the floor is a deep pool and part is not(or perhaps with floating platforms in the pool?) a goal on each end of the field and a mixture of players: some with fins, and others with wings

I mean tackling eachother will probably be good at keeping bone density high, though I'm not sure how hard it is to treat a probably inevitable fracture on the moon?

Closest I can recall is Arthur C. Clarke's "3001: The Final Odyssey". People strapped on wings, flapped their arms, and that was enough to fly.

Alternatively, in "Rendesvousz With Rama", he envisioned a human-powered flying bike. IIRC, a foldable sports bike with wings and a propeller.

It doesn't even require creativity - I think many existing sports would be fun in low gravity. Basketball with extremely tall hoops. Tennis on a massive court. Not to mention golf.

Well, running on a flat surface is kinda hard in low g, so I guess you'd have to make some adjustments for that. But yeah basketball where players jump to the ceiling and then push of from the ceiling towards the floor could be quite crazy.

I'm kinda thinking handball would be insane, tho I wouldn't wanna be the goalie

Slamball would be a sight, that's all I can say.

Lunar no-atmo base jumping. See Mons Huygens as few have.

This is either suicide with extra steps, or loads of fun!

The line between those 2 is surprisingly thin!