Just saw this mode at fileplanet, thought you might be interested. Its a mod that makes those sentry bots follow you around the entire game. I know someone said that they were having trouble at certain point, im sure this will help alot since those bots kill everything with a few shots. here it is
http://www.fileplanet.com/files/140000/143914.shtml Just extract to the base folder and then type spawn char_sentry in the console.