
Its called a bush axe, also known as a Briar Axe or a Ditch Blade. You can find them at your local home improvement store, and they are one scary sumbitch
I'll let the lowes website explain it
"Known by many names, it is a formidable tool made for serious brush removal. It looks a little like a battle axe and deserves caution and respect."
They also used to give them to people in Prisons for them to clean the yard
These and slingblades...
but they werent allowed to use the files xD