Cowboy Magic Detangler
This is absolutely the best detangler you can buy. It takes out the toughest snarls and does not leave the tail limp or greasy looking. It is rather expensive, but the cheapest place I've found to buy the big 32oz. bottle is petvetsupply.com It is $37.50 and every other website of checked out is around $50. Try it, you'll be hooked!