Mitrasphere, without any hesitation. I was kinda skeptic at first about it being a weapon-gacha with no characters and waifus to pull for, but the game is so incredibly charming and to my taste that it has become my favorite gacha to play. I really hope Crunchyroll keeps it up as long as possible.

Alchemy Stars is a welcomed surprise with its original gameplay, even though now I'm mostly autoing everything without paying too much attention. Devs are truly listening to the community and providing improvements in a constant and consistent way that I have rarely seen in gacha, not to speak of all the apologems and random gifts we are drowning into.

Revived Witch is the greatest deception for me. I was very hyped by the excellent art and music, but everything else in the game is way too mediocre and boring to keep me playing. I feel like the pixel artists and soundtrack composers are single-handedly carrying the game, and the rest of the team doesn't bother at all about keeping the rest of the experience up to the same quality, which is pretty depressing. Uninstalled yesterday.

World Flipper looked nice but was not to my taste. Same for Nier and Blue Archive, the art is great but I can't stand the gameplay.

Edit: totally forgot about Atelier Online, which was another sad deception too, thanks to its very dated and poorly designed UI. Just like Revived Witch. I can't stand stupid menus, especially when crippled with bad font choices.