idk if this is useful in a normal round because i dont use it much but there is a glitch that makes u float (you cant move) but float. Simply press W+S or ur foward and backward keys at the exact same time in mid air and voilia! U FLOAT!
Very useful as a sniper. Simply jump off of some very high place and freeze in mid air and snipe away! If you want to get down tap the crouch button fast and you will start to lower.
NOTE: IN TWO TOWERS IF YOU DO THIS OVER WATER AND THEN CROUCH YOU WILL DIE!!!