Avocados would be dope! Probably strawberries for me though. I hope they add bush/vine fruit in the next game so we can have grapes, watermelons and berries.
If I could have any fruit as my native I think strawberries or bunches of grapes would look really cute. My favourite fruit is actually peaches, but since we already have that in game i'd have to say those two. However, I still think there's room for an alternate version of the peaches in game where they look more realistic. Kinda like the perfect apples or lychees. (Imo i don't think the perfect peaches are all that nice but idm them.)
I love the idea of bush fruits. Blueberries, raspberries, and blackberries are just a couple of options. I could totally see them being native fruits. Plus imagine how cute it would be if your villagers would pick berries!
I have apples as my native fruit, but I've always wanted peaches because they're so cute and I like them in real life more than apples. A lot of people were saying fruit that does not actually exist in the game, so I'll do the same! I think it would be nice to have either kiwi or grapefruit- so cute, right?! And I agree with the other comments- seeing villagers picking berries would be really really adorable!