As a disclaimer I've always been bad at saying "top 1" choises, but I also have an absolute dogshit memory. As expected from my answers this is long.

For non-reimobs (but I view all with the lens because I can), I really enjoyed The Times They Are a Changin'. It's so fucked-up and dark. It's so well-written. Bad things look better just to get 500 times worse every time you think they can't get worse. It's open-ended. It haunted my thoughts for months after I read it and made me cry by thinking about it for a while after. I love suspence and dread and tragedy that lingers with you so badly it makes you nauseous, things you have to consciously open and look at, things you connect only after you sit thinking about them. This, too, is reimob to me.

In reimob Causeway is probably a common nominee and that's because It's So Good. The slow, perfectly paced and built tease for more, descriptions of physical contact and the feelings washed up by it, the slowing and snapping and rolling of heat and hunger and emotions throughout, explicitly horny over each other, over Reigen having wanted Mob from meeting to present...!! Listing it here made me go reread it and I feel l like I'll fucking explode. I can't write with that kind of restraint because I'm impatient when I'm writing but reading it is the BEST. Every chapter that draws things out is a blessing.

Overgrown Lapdogs and their Morbid Curiosities has been one that makes me rush to Ao3 with any updates too. I never really cared for the larger part of BDSM before, but learning about things within that subject in a fic setting is fun. And I love to see those idiots stumbling their way into lovers. Ekubo's dynamic with them both is hilarious.

For oneshots I've read Can't Help Falling in Love With You often just for their silliness. Sunscreen Shame is also really tasty, so shameful, so debaucherously heated... Honestly I've read Pipeworks a lot of times too.

Relic is a dark one, hitting that tragedy aspect with so much love entwined with it. The Bullying Mob Via Time Travel, Sorry -series, Body and Spirit, and Doghouse are some with darker kinks(/tops) I've liked.

I don't think there is a type to fics I enjoy reading. Mob has broadened my horizons a lot.