Quake / Quake World was really the epitome of "not how it was intended to be played". It introduced zigzag, wallhug and bunny jump through some clever exploitation of game mechanics, and completely changed its game play plus that of future fps games of the time. And people would just come up with stupid maps where you could do fps-parkour. I often did it myself for hours on end, just jumping around a map alone or with friends while chatting or listening to music.

A very short demo of how crazy it could get, speed indicator top right. 320 was the default movement speed.