District 9

Aliens in films usually fall into the cute or the fearsome camp. Well, you certainly can't describe the aliens in District 9 as cute. They are derisively called "prawns" by their reluctant South African hosts and are an unsightly mix of insect and crustacean, with a language that consists of clicking noises (helpfully subtitled!) and a liking for cat food. As for fearsome, they are definitely capable of violence but they are more pathetic than anything. They aren't bent on world domination and seem to have stalled their spaceship over Johannesburg by accident. Humanity, of course, reacts with its customary mistrust and herds the visitors into the eponymous District 9. 20 years later, they are still there but about to be moved to what looks suspiciously like a concentration camp.
You don't have to dig too deep to unearth a wealth of political subtext. The setting immediately brings to mind the apartheid years, with District 9 being nothing other than a township. Not that the aliens are merely standins for the formerly oppressed black population. In the opening "documentary" scenes, we see black as well as white heaping all kinds of vilification on the prawns. Rather, they come to represent refugees more generally and the hatred and distrust they receive.
Wikus, our not so heroic "hero", is a typical bureaucrat, working for the sinister MNU. He's only interested in getting the prawns to put a mark on consent forms in order to evict them, and gleefully witnesses the burning of a alien eggs. It's wonderfully ironic that an accident results in Wikus gradually transforming into one of the despised prawns. Cronenberg would be proud of the subsequent body horror scenes, though the real horror actually resides deep in MNU HQ, where the hapless aliens are the subject of experiments in an attempt to access their weaponry which only works with alien DNA.
Wikus might reluctantly join forces with alien Christopher Johnson and his son Little CJ. initally in an attempt to reverse the process of transformation but the film resists making him immediately sympathetic. For much of the time he's clearly acting out of (understandable) self-interest and ignores Christopher's plan to reactivate the mothership in order to return home. In fact, he comes perilously close to completely destroying this one last chance for the aliens. And yet, by the end, Wikus *has* learned the value of self-sacrifice, at a huge cost. Unlike the vast majority of Hollywood sci-fi, this is a film full of ideas as opposed to the Michael Bay approach of ever louder and bigger explosions. There *is* action and it doesn't stint on the gore - both humans and aliens are literally blown to pieces - yet much of the second half centers around Christopher and CJ (he isn't exactly cute either but you do end up thinking that he's rather endearing) and the final image of a fully transformed Wikus crafting a metallic flower for his wife is deeply poignant. Luckily there are enough plotlines left hanging that just beg for a sequel and this is one of those rare occasions when it really seems like a good idea.