An older series (2005) that I watched on an acquaintence's recommendation. It was recommended glowingly, and I understand why, it has interesting characters, a lot of intrigue, some delightfully grotesque moments and a lot of mature content.
In short, an ex-war photographer gets involved investigating some strange exclusive club for the exceptionally rich, and winds up getting kissed by their 'goddess,' which gives him the power to blow things up with his camera. Rather than going 'this shit is awesome,' he instead tries to find a cure, and along the way agrees to try to give the goddess her first taste of real freedom, trying to save her from her abusive mother and the criminals who run the club. We soon learn that her kiss can bestow superpowers, and the club calls in debts to various empowered sybarites to try to hunt the pair down.
The plot thickens and thins in several places, and while it slows down a few times it keeps rolling and reaches a quite satisfactory conclusion. It's certainly entertaining.
On the negative side I'd the mature content is used to an extent that is probably unnecessary. The personalities of and relationship between the hero and heroine is rather dry and they both receive no development outside of their relationship.
The series reminded me a lot of Blood+, for taking a somewhat supernatural idea, playing with it, applying pseudoscience to vaguely explain it, and taking a little bit longer than it needed to tell its entire story. The animation style and the long-term development of secondary characters also resemble Blood+, on the more positive side.
If you're interested in some fairly graphic violence and a well told action anime (and age differences don't squick you too badly), Speed Grapher is a pretty good story. If cranial explosions, humans distending and worlds where the majority of people are just awful bother you, it's probably not for you.
