cl_crosshair_sniper_width <pixels>
Sets the thickness of the sniper scope crosshair lines, in pixels. 1 is a single-pixel hairline; higher values make the lines thicker.
Examples
cl_crosshair_sniper_width 1 - Single-pixel hairline (default).
cl_crosshair_sniper_width 2 - Slightly thicker scope lines.
cl_crosshair_sniper_width 4 - Much thicker scope lines.