I played it back in the day, the first game, when Maiet still handled it before they sold the rights to ijji. I remember the GunZFactor forums were quite popular. Personally, I wasn't very good; I was mostly a mindless "sprayer." There were players performing insane "k-style" moves that were way beyond my skill level. If they got in your face doing that butterfly move, it was all over.
The thing about GunZ was that most of the moves players used weren't intentionally designed by the developers, I think. People just figured them out, and the developers never fixed them, so they became a significant part of the game.
Gunz2 I remember watching the gameplay by steparu a million years ago, something like this:
And thinking, "oh man" this is gonna be huge. But by the time I got to play it, it was already a dead game. I think it never cached on precisely because they removed the glitchy movements that made the first game great.
Maiet also released a MMORPG i loved back in the day called RaiderZ.
Both RaiderZ and GunZ can still be played in private servers, but they did not age very well compared to the beast games we have nowadays.