My friend and I are watching One Outs together - she's quite familiar with this series, both the manga and the anime, while I'm still completely new to it. It's a very... clever baseball-centric story with a ruthless, cynical and devilish protagonist, Toua Tokuchi. Appearance-wise, he resembles Yoichi Hiruma from Eyeshield 21, but I suspect that Hiruma is... less scary, actually, and less mysterious. Not that I know much about Eyeshield 21, but it seems so to me. Besides, One Outs is seinen, which is traditionally harsher than shounen. My current favorite character, however, is not Tokuchi (although I do like him a lot, he is simply too fascinating and I'm convinced that he is Satan in disguise) but Itsuki Takami, a prodigy from a rival team. Incidentally, he is voiced by Masaya Matsukaze, who is also known as Teru Mikami in Death Note.
I didn't recognize him at first, shame on me. It must be fate, folks. Sadly, the fandom appears to be small and not especially active. But I won't lose hope.