A couple friends in highschool introduced me to the game via a private server called EuroGunZ. It removed MTX for gear which more or less eliminated the P2W aspect that plagued retail. I remember being intrigued by it being third person and having an art style that stood out to me more. My friend challenged me to a 1v1 right away and said "I won't even fire my guns" and I thought he was fucking with me. Promptly got decimated, which is when he told me about K-Style. Spent many hours grinding away at learning how to do it and even broke my first keyboard because of just how much APM it requires alongside me always being oafish and heavy handed when pressing keys. Ah memories :')
Game is absolutely timeless, though it is obviously super intimidating for newcomers to jump into the private servers. Honestly you can learn some basic K-Style techniques and hang just fine in most FFA lobbies (by which I mean you'll get a few kills and won't feel helpless). If you do wanna take the next step it is worth it as the act of K-Styling is unlike any other game I've played and feels just as fun as flexing your mechanical skill in a game like Melee does.
EuroGunZ also had a super sick soundtrack full of trance bangers! Not sure what other servers did for music but I'm eternally grateful for EuroGunZ introducing me to various styles of EDM.
I also got into S4 League, which always drew comparisons to GunZ for being a stylish F2P third person shooter. While it dropped GunZ's more gritty, muted art style in favor of more bright and overtly sci-fi anime aesthetics, it was still a treat! I played that on retail servers. It also had a fun as hell soundtrack, this time full of original tunes!