I figure I'd like to bring to light a very small portion of TF2's community, and that is the surfing community. Surfing started a few years back in TF2 when some fans who knew a little bit about the game's physics started making maps.
And that was, when you jumped on a slanted edge, you slid downwards. But you could actually still control how you moved and not actually slide off the ledge and onto normal ground.
Surfing uses an understanding of TF2's movement mechanics to create obstacle courses and sort of race track ish maps.
If left on a continous ledge, or a downward slope, players could gain incredible speed. The more speed they had, the less control they had to make on the fly insane adjustments. A small twitch on the mouse or controller stick could send you in any direction.
Some players, like the one above, have taken surfing to almost proffessional levels.
Figure'd I'd share.