First: Iron Man
. Normally I'm a fan of simplicity, hence my votes for 2 and 3, but this class is simply awesome. It defines what I want to be when in heavy armor and covers a whole bunch of possibilities. And if I ever want to be a battlemech in D&D (more often than I'd like to admit), this is where I'd turn.
Second: Swift Kinetic
. This was really close with 3rd place, but I chose this one because it offers more content, though it can use a little refining. This also covers a lot of build concepts and offers a lot of versatility.
Third: Rocket Knight
. Only third because it is 5 levels and thus more limited, but still very well made and a class I'd love to play. Also complements the Iron Man and Swift Kinetic well.
MLTSP: Swift Kinetic
. Really hard to pick, but I'd choose the simplest entry here, despite them all being fantastic.
All the entries were really high caliber, I feel sort of guilty picking only three