Surf.
Created in 2004 by Charlie Joyce (Not on TF2 tho...),
The first surf map I've played is "Surf_ski_2", on CS 1.6 in 2010.
When I saw that you could surf on a Free2Play game (that required Steam) I downloaded it and start to browse for surf servers. (That's the first thing I did after the tutorial)
I joined a popular Linear surf server, but the gameplay and the feeling of the surf was completely different to Cs 1.6.
Then I searched for more servers, likely combat ones, where I ended up on Wonderland.
So, Surf made me come here, Surf is good and surf is the reason I have 2k hours here. (Including Trade Plaza)
I suk on normal gameplays and the only reason I mained sniper was because I would easily go behind walls/above ceilings or on a tower to get eazy kills or as a spy to get eazy backstabs while sliding on a ramp.
But with time, surf servers were starting to die. It is not the same as it was 2 years ago or like in CS, 9 years ago.
It's sad to see that people didn't mention Surf. Well because it requires skills.
(I don't even have 30 minutes of jb gameplay here. lol)