Simple crosshair script

Hi! can any body give me a simple crosshair script for a FPS? I would like one that you push down the left mouse and you go ads, then you let go, it goes back to normal. I don't want to download the fps package. If its possible, can you post it in your answer?? Thanks for your time. is a very handy tool if you want to rip off peoples scripts.

But if you want to make your own, please go around and watch/read/do the tutorials =).