So you've seen most of the good gateway anime and popular shounens (excluding One Piece and Naruto), I don't watch much of that genre, but one good shounen I've seen is Magi (
http://myanimelist.net/anime/14513/Magi:_The_Labyrinth_of_Magic). It's got some good characters and interesting thematic elements. I'll also recommend Trigun (
http://myanimelist.net/anime/6/Trigun), a fantastic action anime with great characters (and the coolest MC since ever), and some really intriguing sci-fi elements. It starts off a little slow for the first 10 or so episodes, but after than gets much darker and more interesting, and it explores some interesting themes. They're both on Hulu, but Magi is also on Crunchyroll, and Trigun is availible (legally) subbed on YouTube, though personally I'd highly recommend watching the dubbed version as it's fantastic.