Of course, all of the games are fantastic in themselves, but my vote goes to Justice for All. Yes, the one with the least votes.
Sure, it's got some characters you wish Capcom never created (Moe the Clown, Ben and Trilo...), but most of the cases were very creative and all tangled up, like it should be in Phoenix Wright. But the main reason i voted for JFA is because of the final case. "Farewell, my Turnabout" is the name of it, and I was blown away by it. There's plot twists everywhere eventually. Play it, and you won't forget it.