cl_pitchspeed

With cl_pitchspeed you can increase or decrease the speed of your look when looking up or down (with mouse or keyboard).

Usage:
/seta cl_pitchspeed 140

Values: “0” to “140”
Default: 0

Note:
This can help when you go for head shots, so you can easily move the mouse in the head level into left and right.
Most of the servers has restriction on this setting so when you connect into a server just type in the console: /pb_cvarlist and it will give you a list of the restrictions (pb) of that server.