In Global Warfare (mod for Half-Life), the crosshair is very neat : It is made up of different "crosshairs" of different colors entangled together.
When I used to play Counter-Strike, I'd bitch for hours on end about how I couldn't see my crosshair in certain levels like DUST.
The Global Warfare crosshair fixes all of these problems.. it works remarkably well !
Just thought I'd rant a bit
