Everyone really did a commendable job on this one, and I think everything you all got is correct, so it's only a few you are missing. Lots of interesting ways to approach this, some people maybe spent more time than one would have expected rather than taking some more hints - some of the categories weren't intended to be easily guessable without a hint.
I was quite impressed you almost got all the moons at the end here, that was that set, major moons of Mars, Jupiter, and Saturn, a hint would've been something like "Ganymede."
(2) actually was one of the much simpler ones. It's just large European capital cities - London, Berlin, Madrid, Rome, etc...
(15) I got some complaints from dead folks too, it was a small set so that's a problem. All I was after was the metals Copper, Silver, Gold, and Platinum, kinda precious/well-known metals and in the order you'd see them for various rankings or awards or whatever sometimes.
(11) is what I would admittedly say the worst, and a bit of filler - as I mentioned again on the dead QT in setting up this puzzle for today, I'd completely forgot I lost any notes I had on the original version of this puzzle, and didn't remember all the sets of words perhaps. This one was entirely a recent add-on in other words, and it's not an obvious set of names or group of something per se. Hopefully with a hint like "hobbits" though someone could have started working out...
Fantasy (more specifically kinda Tolkien though no berating folks on Tolkien knowledge here

) races:
Men, Elves, Dwarves, Hobbits, Orcs, Goblins, Ents, Trolls, Wizards
That leaves (9) which is just the tf2 classes, really a hit or miss but I know some folks play the game, realized it was some of the dead laughing at this one more, but still, again a hint could've set people on the way if it was needed here. That would be Scout, Soldier, Pyro, Heavy, Demoman, Engineer, Sniper, Medic, Spy