Try and think of as many as you can, sorted from most-needed at #1 to least. List them according to your generation, rather than trying to guess what the newfangled stuff would be.
#1. The Fisher King. #2. Star Wars. (TOS) #3. Memento. #4. Boondock Saints. #5. The Princess Bride. #6. Spirited Away (Sen to Chihiro no kamikakushi) #7. Battle Royale. #8. Infernal Affairs (Mu Jian Dao, the original “The Departed” - and yes, the translated pun is horrid, but the film is brilliant. #9. Serenity (& The Firefly Series) #10. The Big Lebowski.
If you’ve seen 3+ of the above, I will automatically like you and attempt to push other obscure and semi-obscure films, books and comics upon you. (The hook is the introductory copies of Gaiman’s “American Gods” and Terry Prattchet’s “The Night Watch.”)
I am not a geek, apparently. Or not of the species of geek most common here. This is a good thing, IMO. To be my kind of geek, one must love these movies:
Monty Python (all of them)
LOTR
Princess Bride
John Hughes films
Sherlock Holmes movies (Basil Rathbone, you bad boy!)
Harry Potter
the Buck Rogers movie made in the 1980s (or was it the 1970s?)
Fred and Ginger movies
Marx Bros movies
Father O’Malley films
some Star Trek films
Wanna make something of it? An enjoyment of musicals wouldn’t be amiss, either.
The Kids Are Alright
Tommy
Quadrophenia
Tommy/Quad Live
Live at The Isle of Wight
Royal Albert Hall 2000
Live In Boston
The Vegas Job
The 2006 Encore Series and, the just-released-today 2-DVD set of Kilburn 1977/London Coliseum '69.
(I started writing a list, and then I realized that they’re all great over and above their geekiness. These aren’t just lines that you repeat to your friends (“I am not left-handed.”); these should all make a geek do more than just laugh. Surely, someone else’s list would be different.
Brazil (all Terry Gilliam, really) Metropolis Dr. Strangelove, or How I Learned to Stop Worrying and Love the Bomb The Right Stuff (Apollo 13 is also good, and may be more geeky) L.A. Story (a love story with geek trappings)