1. Dune.
Love it, hate it? It’s the champion. Nothing else comes close.
2. Farenheit 451
Dystopia at its finest.
3. Planet of the Apes
Heston’s film is better, but this a masterpiece.
Honorable mentions: Cat’s Cradle, Lord of Light, 2001, Brave New World, Foundation
I always thought it was an incredibly effective summary of strategic thought for those who are outnumbered. Whether it is war, politics, or whatever, just because you are currently powerless doesn't mean you are destined to lose. You must think carefully, be patient, and come up with a damn good plan. Trying to do it all at once is a guarantee that you'll lose.
Roger Zelazny really is one of the truly great writers, regardless of genre.