The Departed (2006)
Leonardo DiCaprio,
Matt Damon,
Jack Nicholson,
Mark Wahlberg,
Martin Sheen,
Alec Baldwin,
Vera Farmiga
Remember, you're voting purely for the group of actors involved, not for the best film. Because, given the chance, you would, of course, make a much better job of it in your production than some of the directors did in these films!
The possibly even more impressive casts of the Harry Potter films, The Lord of the Rings and Hobbit trilogies and the Batman/Dark Knight franchise are beyond your means, because even an unlimited budget has its limits... ;-)