I found a crazy "Fast running" Bug.
If you walk and hold the running key to run you will walk faster, BUT if you hold walk(w), sprint("shift") and [2 options :]...
[1]...and hold the button to move right(d) and move you mouse a bit to the left and adjust you movingway ...
[2]...and hold the button to move left(a) and move you mouse a bit to the right and adjust you movingway ...
... you will move even faster than running