Welcome to the AndroidForums, ajgmcse.
I'm thinking you might mean a task killer...?
If this is the case and you have an Android device running Android 2.x or higher, then I would strongly recommend against such a thing. Android does a great job on its own of managing tasks and memory.
If you really need to kill a task, your phone already has this ability: menu -> Settings -> Applications -> Manage applications -> select your app and hit "force close".
Failing that, you can search for this type of app on the Android Market under "task killer".
Good luck and again, welcome to the AF!