This is one of my favorite lines in a movie. This soliloquy was spoken by Roy Batty (played by Rutger Hauer), the replicant in Blade Runner.
I've seen things you people wouldn't believe. Attack ships on fire off the shoulder of Orion. I watched c-beams glitter in the dark near the Tannhäuser Gate. All those moments will be lost in time, like tears in rain. Time to die.
This line wasn't originally on the script but Hauer improvised on it.