[KillerGremlin]

I want to add to my FPS list that certain games like Counter-Strike, or even sniping in Halo or using the Rail Gun in Quake 3 come down to very precise aiming. These are games of pixels, where moving a millimeter the wrong way will be the difference between a headshot and a miss.

You can calibrate a mouse, and to a less extent an analog stick, to have very dull sensitivity so that you can have very precise movement. When you watch the Cal League Counter-Strike players you see them moving their mouses A LOT. This is because the sensitivity is so low. The advantage is that when you are making precise, surgeon-like shots towards someone's head, you can accidentally twitch or move too much and still make the head shot.

When sensitivity comes down to my entire arm or hand, as in the case of using a pointer device, there is way less ability to accurately point.

You don't write with your whole arm, you use your fingers and wrist. Precision movements just seem to be inherently vulnerable to large sweeps of an arm.