Rent-A-Goat is awesome. They are excellent for clearing brambles, thorns, blackberries, and ivy off of steep slopes, where mechanical removal would be very difficult and expensive. They set up a temporary fence around the area, lock a few goats inside, and leave them for a few days. For large areas, they deploy a whole herd, complete with goat herders...450 goats can clear an acre a day, according to the website. All the brambles are completely gone, roots and all, and the goats are fat and happy.
My company has used them in the past to clear out blackberry brambles from an abandoned house. It had an overgrown, steeply-sloped backyard (nearly a 1:1 slope) with old lumber, appliances, and other junk all tangled up in it. Rent A Goat came by, set up a temporary chain link fence, and put five goats inside with a little pop-up shelter and water trough. By the end of the week, that slope was
completely barren. And fertilized. It would have taken twice as long, and cost twice as much, to clear that backyard otherwise.