Avocado is a good one. It really is unique. Not many fruit with that high of a fat content
Personally I'd say natal plum. Which I've mostly just foraged from the landscaping that uses it liberally in SoCal.
Weird Fruit Explorer did a video earlier on with his top 10 "weirdest":
https://www.youtube.com/watch?v=TA4kIQqX2I0-
jentik (
Baccaurea polyneura) describes the flavor as "salsa". Tomato-y with additional savory flavors like onions and herbs and a slight spiciness and even limey. Phyllanthaceae family has quite a few other edibles.
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velvet apple (
Diospyros blancoi) a persimmon. Described as mango yoghurt. Flavor seems to vary widely based on growing conditions. Ebenaceae is the family persimmons belong to.
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dabai (
Canarium odontophyllum) "buttered carrots and olives". Burseraceae is the incense tree family.
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engkala (
Litsea garciae) "Avocados and buttermilk". Lauraceae is the laurel family.
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durian (
Durio spp.) Malvaceae is the mallow family.
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banana varieties (
Musa acuminata) FHIA-18 and Pisang Kilang. Musaceae is the banana family.
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noni (
Morinda citrifolia) Rubiaceae is the coffee family.
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peanut butter fruit (
Bunchosia glandulifera) Malpighiaceae family also contains acerola and many hallucinogens like caapi.
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ginger fruit (
Zingiber spp.) the Zingiberaceae family also contains turmeric, galangal, grains of paradise, cardamom and many more.
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santol (
Sandoricum koetjape) The mahogany family (Meliaceae) also includes neem, lanzones, and chinaberry