Simple hold to zoom, release to zoom out script with intresting crosshair changes when the weapon is shot. Has a nice feel to it ;-)

Just stick it in your autoexec.cfg file. If you dont have one, copy and paste the config.cfg and rename the copy autoexec.cfg. Open the autoexec.cfg file in Notepad and delete the contents. Then copy and paste into the autoexec.cfg the contents of the zoomin.txt file on this page. Then fire up Sauerbraten and enjoy.