Manderlay had an unusual gimmick, though I don’t know if it was unique. No sets, just tape on a ground identifying what was supposed to be there.
Scott Pilgrim vs the World has a very distinctive style. Interestingly, if you really look at it, it almost took the exact same approach to adapting a video game heavy comic as the 1960s Batman series did – with all of the weird, literal adaptation of putting words and other comic-necessary things on the screen. There really isn’t much, if anything, separating Kim shooting herself with her fingers and a BLAM! appearing on the screen, and Batman cheesily superimposing “BAM!” and “POW!” on the screen when people punch each other.
Still, between the weird comic stuff and all of the quick, hard cuts in the movie it’s very distinctive. One criticism I will give though is that sometimes its style gets very… confused with itself. There’s one isolated scene I always cringe at that has a “live studio audience” of sorts, where there are prerecorded tracks of laughter and whatnot behind it. It’s just… kind of there. It doesn’t really work, it’s never mentioned. The scene itself isn’t really even that bad except for the bizarre stylistic shift for those 5 minutes.
I wish I could like this movie, but I had to see Lola Rennt literally 15+ times over 3 years of German and movies begin to… grate on you after you’ve seen them that many times. 
At least I’ll always have that narmtastic die Tasche scene.
The Mask
As much as I like this movie, I have to disagree. The production styling of the movie was based on Tex Avery cartoons, thus the film’s style isn’t unique, and it wasn’t even the first live action movie to ape cartoons of various types (The Villain, Batman, Popeye, Who Framed Roger Rabbit?, etc.).
It is a great movie, and it is very good at what it does, but it isn’t unique at all.