I don't have only one favorite quotation, so I feel like I could give quotations that both define myself and my conception of anarchy.
Also maybe it would be a bit different from the rest as most of the quotations are from individualist anarchists.
I like this one very much, and also the science-fiction novel it comes from.
“We have nothing but our freedom. We have nothing to give you but your own freedom. We have no law but the single principle of mutual aid between individuals. We have no government but the single principle of free association. We have no states, no nations, no presidents, no premiers, no chiefs, no generals, no bosses, no bankers, no landlords, no wages, no charity, no police, no soldiers, no wars. Nor do we have much else. We are sharers, not owners. We are not prosperous. None of us is rich. None of us is powerful. If it is Anarres you want, if it is the future you seek, then I tell you that you must come to it with empty hands. You must come to it alone, and naked, as the child comes into the world, into his future, without any past, without any property, wholly dependent on other people for his life. You cannot take what you have not given, and you must give yourself. You cannot buy the Revolution. You cannot make the Revolution. You can only be the Revolution. It is in your spirit, or it is nowhere.”
― Ursula K. Le Guin, in "The Dispossessed"
These two quotes by Bakunin :
"I am now convinced that the time for grand theoretical discourses, written or spoken, is over. During the last nine years more than enough ideas for the salvation of the world have been developed in the International (if the world can be saved by ideas) and I defy anyone to come up with a new one.
This is the time not for ideas but for action, for deeds."
in the "Letter to the Comrades of the Jura Federation" 1873.
and this one :
"Who wants to spread the revolution must be frankly revolutionary himself. To rise up [...] , we must have the Devil in the flesh; otherwise we only make speeches that abort, we only produce sterile noise, not acts."
in "The knuto-Germanic Empire".
And finally, this one by phil K Dick, not intrisincally anarchist, but kind of blew my mind when I was a youngster. It's in the text "The human and the android" (1972), that I firmly recomend you, by the way :
"The totalitarian society envisioned by George Orwell in 1984 should have arrived by now. The electronic gadgets are here. The government is here, ready to do what Orwell anticipated. So the power exists, the motive, and the electronic hardware. But these mean nothing, because, progressively more and more so, no one is listening. The new youth that I see is too stupid to read, too restless and bored to watch, too preoccupied to remember. The collective voice of the authorities is wasted on him; he rebels. But rebels not out of theoretical, ideological considerations, only out of what might be called pure selfishness. Plus a careless lack of regard for the dread consequences the authorities promise him if he fails to obey. He cannot be bribed because what he wants he can build, steal, or in some curious, intricate way acquire for himself. He cannot be intimidated because on the streets and in his home he has seen and participated in so much violence that it fails to cow him. He merely gets out of its way when it threatens, or, if he can't escape, he fights back. When the locked police van comes to carry him off to the concentration camp the guards will discover that while loading the van they have failed to note that another equally hopeless juvenile has slashed the tires. The van is out of commision. And while the tires are being replaced, the other youth siphons out all the gas from the gas tank for his souped-up Chevrolet Impala and has sped off long ago.
The absolutely horrible technological society -- that was our dream, our vision of the future. We could foresee nothing equipped with enough power, guile, or whatever, to impede the coming of that dreadful, nightmare society. It never occured to us that the delinquent kids might abort it out of the sheer perverse malice of their little individual souls, God bless them. "
Text can be found here : http://bigpicture.typepad.com/writing/2005/07/the_android_and.html