It's called an edgebug. Basically, you fall and hit the exact edge of a block and it negates all fall damage. This glitch happens in pretty much all Source games. Explanation from SourceRuns, "The engine applies the fall damage if the check of the player is on ground succeeds. Such checks are done at the end of movement frames. When you perform an edgebug, you start in mid-air and end in mid-air in one movement frame, while sliding off of an edge happens in-between. The game never knows if you were on the ground or not, never applying the falldamage."
thanks for DS record @Death . I hope my secret carry Discobomb again, hah again. who challenge carry discobomb?
I remember that round, I had a fantastic play playing afk in the nether it went so well xD Also nice headshot Voca :3