Oo CSS - why didn't I think of that? A good five years or go or so I spent the summer living with a friend and we played CSS alongside GunZ pretty much all day every day. I never picked up CSS when I got home but I'd already been playing GunZ for a number of years before that. I might pick that up again, too, played that for maybe 8-9 years in all. I love that game.
If anybody hasn't played GunZ: The Duel before, I highly recommend that. Low specs, free download via IJJI. It'll be very frustrating at first as pretty much the only people who still play it are pros, and the game is heavily reliant on beneficial 'glitches' known as K-Style/Monk-Style which the community has grown to love. Primarily PVP with a 'Quest' mode for team-based PVM which is better for XP. Obviously PVP is the most fun when you get good at it.
Animé/Third-Person/Sword/Firearm game. Awesome.