I play it on laptop, use little mouse from costco(not a gaming mouse at all), in game I set 2.0 sensivity also crosshair size 1 or 0.5, don't remember, it's half of the default one in size, and make crosshair little more fat. Oh, yea also one of the most important things - change crosshair transparency, simply disable it by playing with numbers, so you will see your crosshair when playing levels like dust1/2. It's just me, you can try some other settings.