Bots serve a variety of functions, but their main purpose is to act similar to human players instead of just normal players controlled by the computer. Below is list of bot resources and a few of the more popular bots for the most popular online shooter in the world, Half-Life. 
 
 JoeBOT - An excellent bot for Counter-Strike.
 
 HPB Bot - One of the top ranked Half-Life bots on the Internet. 
 
 Odd Bot - Simple bot that is best used for Team Fortress. 
 
 Akimbot - One of the best bots for Half-Life multiplayer mods.