For the best accuracy, I use this crosshair:
cl_crosshair_drawoutline "1";cl_crosshaircolor_b "255";cl_crosshaircolor_g "0";cl_crosshaircolor_r "255";cl_crosshairgap "100000000";cl_crosshairsize "3";cl_crosshairthickness "1.65";cl_crosshairalpha "255"; cl_crosshairdot "1"; cl_crosshairstyle "5"
It creates a small pink dot for your crosshair, extremely effective for getting headshots at any distance, spraying with it takes some time to get used to but it eventually becomes easy with it. If you're going to use this crosshair you should train with pistols on pistol deathmatch, or aim maps with AK as it's very good for 1-taps.