1) Keanu Reeves in Speed. When he's in the convertible trying to tell the bus that there's a bomb on board. He writes on a sheet of paper and tries holding it up as a sign. The paper slips out of his hand and plasters itself on the bus windshield which dramatically tells everyone "BOMB ON BUS".
But in the background, you're treated to this wonderful moment of Keanu Reeves falling flat on his face. I couldn't help but laugh.
2) Mel Gibson in Conspiracy Theory. He has a moment where he hallucinates while driving a cab. He's snapped back to reality when he realizes he's driving on the wrong side of the street.
But in the background, there's this poor bastard in the back seat, pounding on the glass, yelling "LET ME OUT! LET ME OUT!"
3) Mel Gibson in Signs. Yep -- he makes the list twice! There's a moment where they know aliens have made it to Earth. They see the saucers hanging overhead, but there's no action. Just a tense ennui. At one point, one of the characters is staring at a cornfield and he picks up a rock to throw it into the cornfield in frustration at the standoff.
I couldn't help but yell "OW!" as the rock flew into the cornfield. In the theater, there were these lovely bubbles of laughter where a couple of people would laugh, but the people around them were too serious to get a good laugh out of it.
4) Hugo Weaving in Fellowship of the Ring. When he says the line "Welcome to Rivendell".
Or, if you're me, you heard "Welcome to Rivendell...Mr. Anderson!"
5) Samuel L. Jackson in Deep Blue Sea. SLJ once again demonstrates his badassery by telling the crew of survivors that they're going to pull together and find a way out.
6) "Rowdy" Roddy Piper in They Live.
I came here to chew bubblegum and kick ass. And I'm all out of bubblegum.
6.5) Matt Damon in the trailer for The Green Zone -- I came here to find weapons and save lives. at 0:28
But if you're zetshia_gudani or me, you hear him saying "I came here to find weapons and save lives. And I'm all out of lives..."
7) Madonna in her death scene in Evita. Her voice cracks and it just utterly destroyed the gravity of the moment for me.
That movie, in general, is hilarious to me. It's a movie by a British director with an American actress about an Argentinian woman.
8) The beginning sequence of Dead Alive.
I really struggled with including this one. The movie seems like it might have been made to be funny. It was Peter Jackson. But the very beginning of it at least starts off like a serious movie. And somewhere in dismembering the explorer, there's a change of complexion in the whole film where you can almost hear the script writer in the background, saying "I'm tired of writing horror! I can do better than that! I'm going to make this...A COMEDY!"