How do i block gangster war on facebook?

[john]

When it pops up in your notifications, just click on the top of the notifications box (not the minus (-) sign)
It leads you to a screen that shows you all the notifications you've recently received.
On the right of the screen, there are boxes with check marks and then the application name.
If you choose not to get notifications from Gangter Wars, just uncheck the box, and you'll never get them again.
(This works for all applications)