Neuromancer: I read this first when I was about 19. I remember being confused a lot by it and didn't really understand what was going on.
This time around, though, it rocked. The story is convoluted and complex, but it essentially follows a hacker called Case who is slowly dying in Chiba - a district of Japan. He is given a second life as long as he commits to an unexplained mission presented by an weird guy called Armitage. Along the way, the plot thickens as Case learns his job is to hack through a powerful AI, and that his real employer is a part of that AI called Wintermute.
Visionary and amazing. Still incredibly powerful.
I want to add to this and say that Gibson's prose is incredibly light (it's not labourious, and convoluted sentences using words particular to this novel just roll off the page), but simultaenously powerful and paced so well, an example:
"Cold steel ice odor. Ice caresses his spine.
Lost, so small amid that dark, hands grown col, body image fading down corridors of television sky.
Then black fire found the branching tributaries of the nerves, pain beyond anything to which the name of pain is given..."
"The landscape of the northern Sprawl woke confused memories of childhood for Case, dead grass tufting the cracks in a canted slab of freeway concrete.
The train began to decelerate ten kilometers from the airport. Case watched the sun rise on the landscape of childhood, on broken slag and the rusted shells of refineries."