Second Peace Maker Kurogane .. the same Shinsingume story with most of the details, characters, and events. As Guardian Enzo mentioned, You'll recognize lots of the details, down to names of organized Attacks ! .. I personally preffered PMK over Hakuouki. Unfortunately though, it included so much less swordsplay, fights, and overall action. But other than that, I found it very nicely done, and quite touching at points. You'll love it.
I can't believe no one mentioned Basilisk ! (stay away from this one if you're not into serious, dark, gory animes)
EDIT: @Enzo: You know what's even better than Kurogane? That nice signature of your's
Definitely the best swordsplay ever drawn on paper !