"The Thing From Another World" (Howard Hawks' Classic)
"Invasion Of The Body Snatchers" (The Original)
"Aliens": What "Alien" Should Have Been!
"It.. The Terror From Beyond Space": The Original "Alien"
"Predator": Cinema's Coolest Alien since "This Island, Earth"!
"The Andromeda Strain": Superb then, and now!
"Them!": B-Movie Perfection!
"The Incredible Shrinking Man": What if...?
"Night Of The Living Dead": Who says it takes a big budget to make a classic?
"Tremors": Guns and commom household chemicals in the correct proportions are goooooood!
"Colossus: The Forbin Project": Computers as Gods
"Forbidden Planet": Shakespeare's "The Tempest" in Space.
Jack.
The only movie that, as a kid, scared the HELL out of me. Other favorites of the horror/sci-fi were "Night of the Living Dead", "Day of the Triffids", "Them", "Last Man on Earth", "Horror Hotel", "Creature from the Black Lagoon" and "The Fly".
OK, with a handle like Jack Deth you have an unfair advantage on this thread.
You and I and any other SF characters should either disqualify ourselves or move into a "professionals" division ;^>