I don't really have one, I do have fruits I prefer over the others. I'd rather eat a banana over a mango, even though I think I like the taste of mango a little more, I still like banana and there's a bit less hassles.
I prefer a pear over apple, I dislike the apple since I was a kid, I don't hate it and could still eat them, but I like pears better.
I like pineapples and strawberries, but wouldn't say they're my favorite, I'd rather eat a pear than pineapples, but I could eat a lot of pineapples at once, and strawberries are definitely better than watermelon to me, but I still like watermelons more than apples.
So yea they're all kind of the same to me, I just don't eat them to save myself some trouble, I would have to go through all of the above if I only have money and have to buy one type of fruit. I could say I like apple the least. I don't know about oranges, I could eat them but I don't think I'm missing much when I don't.