What's it about?

A Japanese sniper who goes by the codename of Golgo 13. The series follows Golgo 13 as he accepts assassination contracts around the world. If you plan on watching it, you should know there are a few iterations. A 1991 miniseries (and movie) and a newer remake from 2009. I recommend watching the 2009 series. The animation and voice acting is better, and the story is easier to follow (it's also longer, clocking in at 50 episodes). Although, the 1991 version is still a cult classic.

I wasn't aware there was a new version, this is literally blowing my mind

Yeah, it's great. Have you seen the Old movies?