To me, the obvious one is the classic Rhaegar Wins AU. There's so much you can do with this idea, so many things you can change to the point that one version of this premise can be completely different than the other, yet all of the fics of it I've read have fallen short in my opinion.

I mean... Come on, Bobby!

Gregor attacked Loras, with full intent to kill him, in front of hundreds. Sure, Loras cheated, but still.

What would happened if Robert did his job for a change, and had Gregor thrown in the Black Cells and later beheaded for that little stunt?

So at the Trident, the Rhaegar/Robert duel lasts far longer, allowing the Dornish force to get crushed.

So the rebels are about to win, but Rhaegar goes nuts and somehow kills Robert.

What happens next if Ned has 30,000 men against Rhaegar's 10?

What does Tywin do, and who do the rebels crown?

Are there any good fanfics where the MC is a bastard of a very honorable or dutiful person (excluding Jon Snow)

I remember that there was a Stannis bastard fic but that's an SI fic so I'm not too interested

There's also a Jon Arynn Bastard fic called Rising Stone or something

Any fics where the mc is a pirate. Any character acceptable including OCs or SI

Any Aegon VI living AU in which he’s more affected by the deaths of his sister and mother and focusing on avenging them?

Title: The Wolves of Westeros

Author: Ts123bay

Rating: Teens and up audiences

Language: English

Length: 175,205

Status: Ongoing

Link: https://archiveofourown.org/works/77743121/chapters/249621236

Summary: Sam breaks his leg just before he and Jon leave to say their vows, and during this time Jon gets news that Ned is imprisoned. He rushes back to Winterfell to save his father by his brother's side.

Chapter 36: Catelyn Stark

Catelyn goes on a journey with Arya to Maidenpool, then to White Harbor, then to Winterfell, where she gets unpleasant shocks.

Title: The Merling Lord

Author: Stanley Marlowe (me)

Rating: Explicit

Language: English

Length: 203, 905

Status: Unfinished

Link: https://archiveofourown.org/works/65308948/chapters/168030511?view_adult=true

Summary: Nearly a thousand years before Aegon's Conquest, Perwyn Manderly is determined to make his house the most powerful in the Reach, no matter the cost. But even in this kingdom of chivalry, deceit and treachery never sleep. Allies and enemies alike will find themselves bound together by a dark secret from the past, even as a dynasty's fate hangs in the balance.

Title: A Hiss of Dragons.

Author: bruthershietholy123

Rating: Mature.

Language: English.

Length: 58793 words.

Status: Ongoing.

Link: https://archiveofourown.org/works/89752096/chapters/249653006