In Bruges
The promo for the movie is insanely deceptive, to the point where I had to search for an alternative cover to not give the wrong idea. Judging by the trailer it seems like they were trying to sell it like a Lock, Stock & Two Smoking Barrels knockoff, but it's not that at all. It's a black comedy and one of my favorite movies of all time. Definitely top 3. I'm a big fan of Martin McDonagh in general, but this is his best film. Don't watch the trailer, don't look at the posters, just watch the movie. It's somber, but darkly hilarious and has such a tightly written script with some deeper themes if you're willing to scratch the surface a bit. It might also be Colin Farrell's best role.
Martin McDonagh's
3 Billboards Outside Ebbing Missouri is also an underrated gem. He's great at writing dark comedy.