As the saying goes, there are always two sides to a coin. I believe that every argument ever made CAN be rebutted no matter how strong or undeniable it is. But, to be able to do this, you need to be able to look at everything from a different perspective. You need to have a wide knowledge.
Anyone else like loopholes? "Can any argument, no matter how well made, be successfully rebutted?" No, and here's why! Successfully- having achieved popularity, profit, or distinction. So when you say "successfully rebutted" you mean that the rebuttal achieves popularity, and is accepted by the general population or group of people. Well... What if someone (a troll) proposed an argument that was "resolved: *obvious statement*" such as "resolved: strawberries exist". Well.. Can you successfully prove that strawberries do not exist? Or let me restate that. Can you prove that strawberries do not exist, AND have the general population believe you? Prooobbbabbly not. You see, nothing is impossible with the use of the English language :)