This app kills minimized app tasks when you turn off the screen.
While the other task killer apps kills service tasks
this one kills app tasks which are opened by users.

When you install this app you can save the battery and memory usage even if launch many apps and minimize them with home button.

NOTE:
This app CANNOT remove other apps from launched app list which is shown when you long-tap the home button. So you cannot see the effect obviously if you don't check the memory usage finely. For it is not desirable or able for an app to kill other apps entirely according to the Android App notions.
But you can see the killed apps takes time to restart when you install this app since the apps' tasks are killed and inactivated. I tested the memory usage and I found out that Auto App Killer can surely reduce the memory usage.