Pacific Rim also makes great use of its aspect ratio, to make the mechs and monster look HUGE.
Speaking of monsters, perhaps Monsters (2010) would be my suggestion.
It gave the director an in-road into the film industry, and is broadly appreciated, but it didn't redefine filmmaking in the way the crew thought it would.
Made for less half a million, the techniques used in the film to make it look more expensive weren't adapted as widely as presumed.
It's a shame, because now all movies seem to look very low-budget or very high-budget, and the mid-budget film has all but disappeared. This offered an opportunity to provide a mid-budget-looking film, without the struggles for financing. It's possible, though, that Edwards' next film (The Creator) will take advantage of his previous work, and the studios will produce some new IP without the $200M risk that's usually associated.
Not complaining, but I think I prefer the poster on this Wikipedia article than the one posted.