Hrm...list of favorite shounen manga, huh? :)
Record of a Fallen Vampire. Vampire shounen is rare, but when it comes out in this form it becomes so beautifully tragic and gut-wrenching and awesome in the fights as well as compelling in regards to the drama and emotions. The pace of the manga isn't extremely fast, yet when it begins one cannot help but hope that it will continue. The entire story is just so deep and full of complicated twists, and wonderfully sad.
Black Cat. Very nicely done, and very great on action/adventure. Also, the tone of the story has some depth to it, just enough to develop into an entire universe that can be very interesting.
Durarara!! I usually don't like city shounen, but this one definitely fascinates. And I love how the "coincidental" events are all linked together.
Fullmetal Alchemist. Awesome and wonderful plot and characterization and depth all around. The characterization and plot is compelling even with the humor, and that makes it all the more awesome. :)
Nurarihyon no Mago. So far, it's doing very well and has a beautiful supernatural side to it, though I would say that the romantic side of it is a bit underdeveloped. That, and...I do hope that the pairings will be developed as deeply as in Fullmetal Alchemist or Kurohime. :)
Kurohime. Definitely may sound strange, since this may show some skin and seem to be a bit fanservicy, but it really isn't. Instead, the romance of the main pairing is just deep and wonderful in such a way that no other manga I have seen around here has matched up to such development and depth in intensity and compellingness.