I'm partial to:
"In order to get what we've got, Anita, we have, in effect, traded these people out of what was the most important thing on earth to them — the feeling of being needed and useful, the foundation of self-respect."
-Kurt Vonnegut in "Player Piano" (On Automation)
"But never have I willfully destroyed a tooth on a gear of my thinking machine. Never have I said to myself, 'This fact I can do without.'"
-Kurt Vonnegut in "Mother Night"
"There's only one rule that I know of, babies—God damn it, you've got to be kind."
-Kurt Vonnegut in "God Bless You Mr. Rosewater"
"There are plenty of good reasons for fighting, but no good reason ever to hate without reservation, to imagine that God Almighty Himself hates with you, too."
-Kurt Vonnegut in "Mother Night"
"If liberty means anything at all, it means the right to tell people what they don't want to hear"
-George Orwell
"Man must rise above the Earth to the top of the atmosphere and beyond for only then will he fully understand the world in which he lives."
-Socrates