If you're like me, you love film. You also love 40K.
Now, as you know, these things have never really come together. Unless you count some embarrassingly cheap GW produced nonsense, computer game cutscenes from the times when dinosaurs roamed the Earth, and that "Ultramarines" film. Which, as we all know, was 22 minutes of story mixed with roughly an hour of Space Marines walking around while supposedly moody music played doing absolutely naff all.
Basically, 40K on film sucks.
Or does it?
The official films are absolutely bloody awful, but there are a number of films that embody the ethos of the setting and are (surprise!) not dreadful. Notice I don't say "good"; most of them are still fairly terrible/ narmy, but nonetheless they are worth your time.
Event Horizon (trailer: [url]http://www.youtube.com/watch?v=OVlnER8SxfQ[/url]) is basically an actual 40K film; the setting is pure future gothic, and it actually has The Warp! It's pretty much the story of what happens when a ship's Gellar Field fails, and despite some terrible characterisation, as well as a few lines they might make you wince in physical pain, I like it. The cast is excellent, the aesthetics are spot on, and it's thankfully a horror film. If you can endure the terrible script, there's a 40K film worth your time.
Starship Troopers (trailer: [url]http://www.youtube.com/watch?v=Y07I_KER5fE[/url]) or "The Imperial Guard fight Tyranids" is the most obvious choice on this list, but I include it in case anyone here hasn't heard of it. It's hilarious from start to finish. Very much a film to enjoy on two levels - either you can love the dumb action, or you can love the biting satire of military culture (or both, which is what I do). It's one of very few films to, like 40K, present a totalitarian regime relatively heroically... which is of course what the Imperium is. If you find yourself questioning "Why are these fascists the good guys?" then this film has succeeded. If you simply love the gunfights, well, that's because they're pretty sweet. And Michael Ironside is in it. If you don't know who he is, you owe it to yourself to find out.
9 (trailer: [url]http://www.youtube.com/watch?v=OnoJecu9e7c[/url]) is a great one for Necron players. Seriously: look at the robots in the trailer! Everything about this film is visually stunning, and for lovers of Xenos: not a single living human. Very dark, very melancholic, and with a wonderful gothic aesthetic.
Battlestar Galatica (trailer: [url]http://www.youtube.com/watch?v=q2x14ZhEc9k[/url]) Yes it's a series, but the pilot isn't. This is very much sci-fi for adults, with a fairly realistic take on a future war - if not the tactics and weapons, certainly the mental and emotional toll. It's also excellent for players of Necrons: the Cylons are very much what the new Necrons are. Seriously, if you hate the new Necron fluff, just watch this and see how far and how brilliantly they can take the idea. It's very dark indeed though: there are episodes discussing the morality of suicide bombing (and deciding it's a valid, heroic strategy), as well as the horrors of the military use of rape. So seriously: not for children at all. However, I would rate it as one of the best sci-fi series I've ever seen, and certainly one of the most consistently exciting.
Dagon (trailer: [url]http://www.youtube.com/watch?v=-yAnVNy27co[/url]) is one for Chaos fans. If you want to get some inspiration for Chaos Cultists, or just why Chaos is so damn scary, this film is superb. It's worth noting that there are a couple of spectacularly gory scenes, but the atmosphere is just superb. Aside from John Carpenter's "In The Mouth of Madness", it's the best H.P. Lovecraft film committed to celluloid, and I recommend it wholeheartedly.
The Mist (trailer: [url]http://www.youtube.com/watch?v=E-NF55EZ5tw[/url]) is another one for Tyranid fans. People are trapped in the middle of a zombie apocalypse... only it's not zombies. It's monsters from another dimension. Notable for one ofthe bleakest ending in the history of cinema; if it doesn't leave you feeling hollow, something's wrong. Also a superb satire of religion - you could argue it's a story about how it feels to be normal people caught between Tyranids and the Sisters of Battle.
These are the films I have off the top of my head (I was going to include "Wicked City", but it's not appropriate on this site). I shall add more later.
What else is there that could be a 40K film, despite there being no 40K in it at all?