Any movie with that THX logo.  I love it!

Over the Hedge - the vending machine.  The rest of the movie kinda lost me.

The one that really made my jaw drop was Pulp Fiction. When the title came up I had no doubt that I would love the film.

Also Star Wars is in good memory for that star cruiser that seems to go on forever...

Saving Private Ryan

I'd add Gladiator to that list

"On my command... unleash Hell."

2001: A Space Odyssey

Patton

just a few, there are many more .....

Amelie
Ghost in the Shell
Appleseed
Final Fantasy: The Spirits Within
Blood: The Last Vampire
Hero
Blade Runner
Master and Commander: The Far Side of the World
The New World

I'll put mine in (not in any order of ranking):

- 28 Days Later (The completely empty city landscape was unnerving)
- Gladiator (Opening Romans vs. the Barbarians battle)
- Hellraiser (When Frank first opens the box and the aftermath...)
- The Host (Come on, how many monster movies completely reveal the monster within the first 10-15 minutes of the movie.  The first on land attack is crazy.)
- Jaws (Who wanted to go swimming on a beach after that!)
- The Last Boy Scout (Okay, not that great of a movie, but it had some good quotable one-liners.  And the opening scene with the football player pulling a gun on the field and shooting anyone who tried to tackle him was pretty memorable.)
- Pirates of Silicon Valley (Maybe only if you're into the Microsoft vs. Apple or the Gates vs. Jobs thing, but the opening 10 minutes showing the contrast of Apple's commercial showing an Olympic hammer thrower putting a hammer through the big screen of "Big Brother" freeing the people and then 10 or so years later showing Jobs on stage with a big screen projection of Gates in the background and how they were now "working together" with Gates looking over him as if he's "Big Brother".  For a Made-For-TV movie, I thought it was pretty good.)
- Red Dawn (The initial attack on the high school by the Russians.  I was in high school at the time the movie came out and it was pretty frightening back then.)
- Saving Private Ryan (The Omaha Beach battle was just incredible)
- Shoot 'Em Up (A lot of people hate this movie, but I see it as the parody of action movies that it is.  Come on, in the first 90 seconds of the movie the main character kills someone with a carrot.  What's up Doc?  The whole movie was a cartoon, but the opening with the child birth and cutting the cord by shooting it with a pistol... complete lunacy, but definitely memorable.)
- Starship Troopers (Just a crazy, bloody battle between humans and bugs...)
- The Terminator (The 2 main guys teleporting in and their different ways going about to get clothing made for an interesting opening.)
- Top Gun (Awesome 80's rock music, slow motion, Navy guys working an aircarft carrier = Win.)
- Troy (Achillies versus the Giant in the opening battle.  You expect this huge long drawn out battle and then Achillies takes him out with one sword stroke.)

I'm sure there's others I missed or just forgot the openings to them.  I could have listed most of the Bond movies since they typically have some crazy opening action scenes, but left them out since I couldn't think of one that stood out from the others.