Melty Blood is a Japanese doujin 2D fighting game, developed primarily by Type-Moon, French-Bread (known as Watanabe Seisakusho prior to 2003), and Ecole. Yet another sequel of sorts to Tsukihime.
It has also been adapted into a manga series, featuring art by Takeru Kirishima and serialized in the CompAce magazine, published 2005.
As of Melty Blood: Actress Again, there are 25 playable characters.
This tag implicates tsukihime (learn more).