Darwin's Game: Started out feeling a lot like Mirai Nikki (survival game with magic powers, main character has a particularly strong one but is inexperienced, psycho love interest), but I really enjoyed where it went over the season. Kaname came into his own as the main character, and the turning point at the end of the penultimate episode when he finally let loose and didn't hold back from killing anymore was a sight to see. Apparently the manga is in its final arc, so fingers crossed they continue the anime adaptation soon.
In/Spectre: A really fun series, though I imagine some people might get turned off from the final few episodes when Iwanaga is destroying Steel Lady Nanase through forum posts. The dynamics between the characters really help it shine, and there's lots of great comedic moments, with just enough stakes to keep you thoroughly invested. I don't know how much of the manga was adapted, but the ending leaves room for more, though the arc's plot points are resolved by the end. Also, dem Nanase tiddies.
Somali and the Forest Spirit: Ho man, this one made me cry so many bitch tears. I haven't gotten so emotional over an anime in a long time, but this one tugged at all the heartstrings. Jotaro's VA was perfectly cast as the Golem, but all the voice actors were great, especially Somali's. Beautiful artwork, absolutely gorgeous to watch. It's an emotional rollercoaster, from cheerful to heartbreaking throughout the series. Obviously didn't adapt the whole manga since it's still ongoing, but it ended at a good spot, again with room for more in the future. I might need to pick up the manga since I enjoyed it so much.
ID:Invaded: I'm still debating which is my favorite anime of the season, either Somali or this. I might just call it a tie, because both are really damn good. I loved how the plot was mysteries within mysteries (who killed Kaeru in each well, the identity of the serial killers, the identity of John Walker, everything surrounding Kiki Asukai), and it was fun to try and work out the answers ahead of time. Since it was anime-original, it was well-paced, the mystery unfolding steadily over the season. Great and imaginative visuals, great cast, and a satisfying conclusion, not to mention an awesome soundtrack. Well worth checking out if you haven't.
Plunderer: It's still ongoing so I can't give a full review, but man, it's not what I expected it would be at all. I went into it expecting a goofy ecchi fantasy show with lots of fanservice, and at first that's what I got (and admittedly there's still lots of fanservice). But when the "demon" coming out of the Abyss at the end of episode 8(?) turned out to be a fucking attack helicopter, I was legitimately floored. The story took an immediate hard left turn and it's gotten crazier since then, with continued revelations about where the Aces came from, what the Althing is, and hints of how Alcian society came to be. It's also fucking hilarious throughout, which only adds to my enjoyment. Can't wait to see more.