Star Wars: Austin Powers 2 (Austin... I am your... father). I'm sure this is repeated a lot. Also of course the infamous "Friends" episode, where Rachel dresses up as Princess Leia with the metal bikini. Even recently I saw an episode of the Family Guy (Christmas special) where Santa blocks Stewy's ray gun, just like Vader does on Cloud City, lol. Of course the SNL skit with Kevin Spacey doing Christoper Walken (she's...fast...enough...for...you...old man) and Bill Murray singing "Star Wars.... nothing but Star Wars" is classic.
E.T.: Naked Gun 2 1/2, when Frank Drebin sends the guy in the wheelchair flying through the air.
Matrix: Well, everything parodied the Matrix it seemed. Shrek had the Trinity-kick in it, Scary Movie had the bullet-time, etc.
The Sixth Sense: The whole "I see dead people" thing seemed to be everywhere for a while.
Titanic: The "I'm flying" scene.
Terminator 2: Wayne's World, the "Have you seen this boy?" line.
The Godfather has been parodied to death in almost every type of media & entertainment
Psycho - The shower scene has been parodied quite a bit Treasure of the Sierra Madre - The "stinkin badges" line Singin in the Rain - title number The Exorcist
Im going to put my 2001 vote up. It was parodied twice in South Park in the episodes Trapper Keeper and Bebe's Boobs Destroy Society. The scenes where a spoof of David Bowman floating in the HAL computer room and when the one ape discovers that a bone can be used as a tool/weapon. Also in Woody Allen's Sleepers there is a HAL imitation.