The Three Body problem. The Lathe of Heaven.
And while I haven't read Parable of the Sower yet, everything I've read of Octavia Butler has ranged from really good to some of my favorite books ever, so I'm sure it's a good one.
One anti-recommendation (kind of): I recently read Finite and Infinite Games, after many (many) recommendations for it, and didn't particularly like it. Obviously I'm in the minority on this, but I really wonder what other people saw in it.