With the GNOME desktop of yesteryear it was easy to add a "force quit" button on your top or bottom panels of the desktop. In Ubuntu with Unity it can still be done and here's how.
You'll first need to open up the Ubuntu Software Center and do a search on "main menu" and proceed to install that. Once installed, click the Ubuntu button at the top left of your desktop and search for main menu and click to start it. Click the "+ New Item" button and create an application like the photo above.
Pick an icon of your choice. On the internet I searched for "pirate icon" to get the skull and crossbones. When you find the icon of your choice, click the empty button on the left area while creating a new item and find your icon you've just downloaded. When done, close the main menu boxes.
Again, click the Ubuntu button at the top left of your desktop and search this time for "xkill", the new app you just created. When it appears in the search, drag it to your Unity launcher on the left as seen in the photo below. Thats it! Anytime you have an application thats misbehaving, give it the ol' pirate XKILL and close out that program not responding.
I wont leave you hanging (or walking the plank) looking for pirate icons all day. Give these a try (right click em to save)....