I don't really watch hella obscure animes, but I'll bring up one that came out like 10 years back just cuz we got some younger people here who may not have heard of it. People talked about it when it came out and then it just kinda fizzled out because it had some issues in production, and that's Blue Exorcist

and I'll be the first to say it's not the "best" anime, but it was one of my guilty pleasure animes where you're just sometimes in the mood to watch something that's fun and kind of trash (but in a great way). Pretty predictable, pretty rediculous, but has a fun cast, the main characters are dumbass twins (love twins) and it has a real late 00's/early 10's quality that I find kind of nostalgic. They nuke hell with a warhead at one point which was absolutely stupid, and I loved it. Pretty sure at one point Satan was shooting Japan with lasers, this anime whips.
What's also fun about this anime is that like 3 years ago it randomly got relaunched, and they decided to undo some of the decisions that the 1st season of the anime made. So if you're a fan of the manga and didn't quite so love how they nuked hell with a warhead--there's also a version of the same exact anime that didn't go bonkers. Fun for everyone.