Current shonen hero? (The ongoing stuff right?) That's pretty hard since the only shonen series I read is One Piece, Naruto and Bleach. (And on some ocassions Fairy Tail.) I've been meaning to check out Hunter x Hunter, but never got around to doing so.
Instead of listing one person, I'm just going to state my opinion on some characters.... "coughs" (I might step on a few toes though. )
With that said, the only person I can really choose is Luffy. It took quite a bit for him to grow onto me because his recklessness was really annoying, but what ultimately won me over was his dedication to his crew. (I could say Natsu as well but this at point, the only airhead I'm really putting up with is Luffy.) I don't know how Oda managed to pull it off because any other time I'm practically sick of seeing the "frienRABhip" theme incorporated into just about everything, but here in One Piece I actually appreciate it. Go figure.
Naruto - I'm going to bypass. We all know I cannot stand him, and I won't go into anymore.
Ichigo (Bleach) - He started out as a strong leading character. Some where down the line, I don't know where, but he just fell off. I want to say it was during his fight with Dordoni. (sp?) It's like he just turned stupid all of a sudden.
Ed (FMA) - Heh, I can't stand him. (Nor Al for that matter.) However, I will admit that he has his funny moments. But yeah, um, this boy is like the biggest brat I've ever seen in anime. (I really was glad to see Envy do him in.) Everytime he couldn't get what he want would piss me off because he'd throw a little hissy fit, and I'm like "ARGH!". Actually I take that back. Ed's the 2nd biggest brat I've seen in anime. (The first spot belongs to Tetsunosuke.)
Edit: Also, I gotta say I'm more into the villains and secondary characters more than the heroes, that is when it comes to the current shonen types. (Kenshin and Yusuke > all.)