XD Oh boy.
Um... outside of Candace/Jeremy, I don't really ship anyone in the show. They're children, after all. I do think Isabella/Phineas is cute, especially since the other dimension movie (can't remember its name) had a huge "throw the dog a bone, yank back the dog's chain" moment within seconds at the end. I was laughing hard and cried at the same time, it was brilliant and jerkish. So... it's canon, but at the same time it's not, which is a bit interesting, honestly.
But otherwise, I'm pretty much indifferent to the pairings in the show. I would probably squeal if Perry ever found a girlfriend/mate, but that's never going to happen.