Daisuke Ishiwatari is a Japanese writer, illustrator, programmer, designer, heavy metal musician, king of serving tea, and Mr. Badguy that works for Arc System Works. His artwork is notable for having a very distinctive rough aesthetic, and his music is known for its intricate guitar work.
His claim to fame is his work on the cult hit Fighting Game series, Guilty Gear, in which he produced the artwork, wrote the story, programmed a good deal of the games, and provided its godly soundtracks. Oh, and he also provided the voice for lead character, Sol Badguy, as well as his past self, Order-Sol (except in Story Modes). As anyone who's looked at the character list or their respective moves knows, it's evident that he is a major rock enthusiast. His favorite band is Queen.
With production rights to the Guilty Gear franchise temporarily lost to Sega, he along with Arc System Works went on to create a Spiritual Successor in the form of Blaz Blue, where Ishiwatari merely provided inspiration, character selection artwork, and produced the sound track. He also provided the voice of Freed in Battle Fantasia, another Arc System Works project.
Recently he provided the soundtrack to Hard Corps: Uprising, and it is still every bit as eargasmic as the aforementioned soundtracks, if not moreso.
A little known fact: he used to work for a little company called SNK, and was one of the main designers and programmers for The Last Blade series. The gameplay of Last Blade would later resurface in the form of Hakumen.