I still think of Pluto as a planet. It was the last planet to be named as a planet, before they started getting cocky about it. I did read somewhere that there was talk of re-classifying it again as a 'Plutoid', I thought that was kinda cute.
To me Pluto is the most mysterious yet under explored planet in science history. Just by the Voyager's fly by we still don't know much about it and hopefully in 2015 we can with the New Horizon's probe. Still to me Pluto is still a planet despite being downgraded to a dwarf planet. Though I have to say it could have meet it's demise by a collision with another planet's moon and that is why the orbital behavior is out of the ordinary not to mention it's size. Heck the asteroid that hit Earth back in B.C. could have been part of Pluto and then there are some craters on the moon that some scientists say it occured around the same time of impact, but that's just my theory. Sorry about that! I just get carried away about this topic. ^_^*
Well by logic i would say Kuiper belt object because some objects seems to be bigger than pluto and were not recognize as planet.
But honnestly i would have prefer to see appear a new classification for planets, you know like the famous class M planet from Startrek
I don't like the new definition of 'planet' involving the orbit etc., what about planets that "got lost", I bet there are a lot of rogue planets (or should I say "very very big asteroids"?) near the galactical center