Pumpkins fit the Fall Vibe. Plus Abigail loves them. You can get a lot of gold from them plain, through Preserve Jars or Kegs (though of course Preserve Jars and Kegs can give you a lot more gold, it's still a solid crop to sell raw).
Sunflowers and Fairy Rose. Their honey sells for a lot, Sunflowers are loved by Haley. Fairy Rose are loved by Evelyn and Jas, they're easy loved gifts to give them. Sunflowers are a double season crop and can potentially give you extra seeds, which is nice.
People tend to buy a ton of cranberries for the harvest (I'll buy a decent amount of cranberries), but I end up buying a ton of Pumpkins.