Giant Flyer: None of the major worlds documented thus far have truly Giant Flyers; some of the ones with lower gravity have some pretty large flyers, but gravity-scaling doesn’t make them terribly strong, rideable, or dangerous.
Well, perhaps I should say terrestrial worlds. A few life-bearing gas giants (and, once the engineers started working on the problem, suns) have Really Giant Flyers, as in whale-sized. Do they count? They’re mostly aerostats, not aeronefs.
And, of course, who knows what those guys who want to reinvent the mythologae the way they should have been will come up with next week…