Worth noting is that the graphic novel was written at a time in which the openly fascist and borderline Neo-Nazi National Front were a highly visible, if minor, force in British politics. Then again, there's the BNP now, so it's not like that much has changed.
John Hurtin a movie about a totalitarian London? Notably, Hurt's presence is a sort of inversion. In the 1984 version of... well, 1984, John was portraying the protagonist, Winston Smith, and thus was a victim of the totalitarian government. In the film version of V for Vendetta, meanwhile, he portrays High Chancellor Adam Sutler, and thus became the leader of such a government.
In a similar manner, Hugo Weaving is in a movie about totalitarianism. However, like Hurt, Weaving is an inversion: In the first Matrix, Weaving played the antagonist, Agent Smith, who had a role in the totalitarian government (initially). In V, however, he plays the protagonist who is fighting against the totalitarian government.
Awesome, Dear Boy: Stephen Fry on being in it, specifically the idea of being beaten up on camera.
Defictionalization: Anonymous has adopted the Guy Fawkes motif for its protests, which apparently tickles Moore enough that he doesn't mind that this is inspired by the movie, rather than the book.
Disowned Adaptation: Moore specifically requested that his name be removed from the film's production after Joel Silver (the producer) lied about Moore's enthusiasm for the shooting script.
Executive Meddling: It apparently spawned the title itself. While the movie was being made, someone thought it would be a good idea to outright lie and say that Alan Moore completely supported the movie. He didn't, and made that fact known by refusing any payment what-so-ever on every movie adaptation of his work afterwards. Good job!
Fake Brit: Both Portman (Israeli-American) and Weaving (Australian). However, given V's cloudy backstory and the xenophobia of the government, V may not have been a native Brit himself. Considering Weaving actually spent a good portion of his childhood and teens living in the UK, his Fake Brit status is debatable.
Meaningful Release Date: It was originally scheduled to open on November 4, 2005 (the day before Guy Fawkes Night/the 400th anniversary of the Gunpowder Plot) but was delayed four months due to Warner Bros. being unsure about its box office prospects.
The Other Marty: James Purefoy was originally cast as V before quitting due to the difficulty of acting an entire film behind a mask. Some of his six weeks worth of filming remains intact, dubbed over by Hugo Weaving.
The Red Stapler: Demands for Guy Fawkes masks for Halloween skyrocketed after the film came out.
Sigil Spam: Norsefire Puts On The Reich well enough, but the filmmakers outdid them at every turn. There are V shapes everywhere if you know where to look. Almost everything in the background is tilted at a 30-degree angle with something identical or is propped up to form a V shape, and character names have as many E's as possible (E being the fifth letter in the alphabet, V being the fifth letter from the end of the alphabet). And if you were to dub the movie in Latin, V would say "Vi veri veniversum vivus vici" more than once.
What Could Have Been: James Purefoy was originally cast as V, but reportedly he wasn't coming across with the right performance and wasn't acting effectively through the mask, so Hugo Weaving replaced him. Some scenes of V in the film are actually Purefoy in the suit and not Weaving, but with Weaving's voice dubbed over Purefoy's.