Last night I watched Hot Fuzz for the second time and found it to be a film that really rewards a repeat viewing. It's almost a textbook demonstration of the Chekhov's gun principle (named after the playwright, not the guy out of Star Trek - that's Chekhov's phaser) which makes it really satisfying the second time around.
The principle basically says that you shouldn't introduce anything into a story that won't serve a purpose. For example, don't put a loaded gun on a stage unless it's going to be fired in the next act.
Hot Fuzz does this brilliantly - pretty much every single thing that happens in the first two thirds of the film has some element that foreshadows something in the final (violent!) act. For example, Danny's drunken trick with the ketchup and fork in a pub is later used to save another character's life; Danny's questions to Nick about whether he's done all the stupid things that cops do in films are all things that Nick will do later on; the sea mine (almost the classic example!); and many, many more examples.
Now I know that many (maybe even all?) films do this to some extent but I'm not sure I've seen it to the same level. And it manages to stay funny throughout.
If you don't believe me, go and watch it. And then watch it again.
And then watch Shaun of the Dead again because it's even funnier.