I don't know about the best or the worst, but I never quite liked the pressure-sensitive buttons on PS2. They sound fine in theory, but in practice, based on my limited experience, it requires too much effort to find the exact amount of pressure needed for what you want to do. I guess this is mostly based on Metal Gear Solid 2, and it could probably be more fun if it wasn't used for such a sensitive action (with automatic weapons, press a little to aim, press harder to shoot). I have a hard time imagining where pressure-sensitive buttons implemented like that could be very useful though, because it's too hard if it's used for something meaningful, and if it's not for anything meaningful, it's just a useless gimmick.
On the other hand, I kind of liked the motion controls of the Sixaxis. It's implemented poorly in most games, but I've seen some good implementations too. I liked it being used for balancing in Uncharted. It's not necessary, strictly speaking, but I feel like it can add a bit to the experience if implenented correctly. Sadly most developers seemed to try to shoehorn it in places where it really doesn't belong, which, I guess, is a sign of poor design of the whole functionality (good design makes it hard to use poorly).







