Not at all surprised to see the opening line from King's Gunslinger in the list. It's almost archetypal in nature.
"The man in black fled across the desert and the gunslinger followed."
Love it or hate it (Dark Tower), that simple line perfectly set the tone for everything that was to follow.
Some of my favorites include:
The sky above the port was the color of television, tuned to a dead channel.
I am seated in an office, surrounded by heads and bodies.
It was the year when they finally immanentized the Eschaton.
This time there would be no witnesses.
(Sources spoilered for those who may want to guess.