So I saw The Avengers · 12:21am May 5th, 2012
Won't give away much, but it had awesome fighting scenes, some funny moments, and was overall a great movie.
Being the loyal brony I am, and finding it a coincidence it was a team of six, I had to crossover the Mane Six with the Avengers.
Twilight - Captain America (Both are unofficial leaders)
Applejack - Thor (Have blond hair/manes and are physically strong)
Rainbow Dash - Iron Man (Cocky and they fly the most)
Rarity - Black Widow (Beautiful and clever with a sense of fashion)
Fluttershy - The Hulk (With The Hulk as Bruce Banner, they are both pretty reserved and when they're angered, shit truly goes down!)
Pinkie Pie - Hawkeye (Last two by default... and they avoid obstacles well)
Of course I don't care if your crossover ideas are different from mine.