You will know, if you've read the last book in Harry Potter, about the Elder Wand. It is the so called "Invincible" wand that Dumbledore obtained from Grindelwald.
However, many see this as a flaw in JKR's writing. How did Dumbledore beat Grindelwald if he had the unbeatable wand? The answer is here:
"What must strike any intelligent witch or wizard on studying the so-called history of the Elder Wand is that ever man who claims to have owned it has insisted that it is "unbeatable", when the known facts of it's passage through many owners' hands demonstrate that has it not only been beaten hundreds of times, but that is also attracks trouble as Grumble the Grubby Goat attracted flies." - Tales Of Beedle the Bard, Pg. 106
