There was also the whole branch of Surfing, which exploited a glitch in the physics engine that caused standing sloped surfaces to generate forward velocity. Flying around massive expansive maps gliding on slopes while blasting people with shotguns was so much fun (or sniping them mid air with an awp).

There was also a whole sub-genre of skill surf, with mechanically challenging courses to complete.

Oh and then kz maps too, which was just for climbing up huge structures.

Good times