Director: Todd Phillips
Stars: Bradley Cooper, Ed Helms, Zach Galifianakis, Ken Jeong, Justin Bartha, Heather Graham, Jeffrey Tambor, Sasha Barrese, Rachael Harris, Mike Epps, Mike Tyson

The Hangover blindsided Hollywood execs and audiences alike in the summer of 2009, laughing its way into history books as the highest grossing R-rated comedy of all time. How? It's simple, really: Prior to its release, the comedy genre was stagnant, devoid of event movies since 2007's Knocked Up. That all changed, however, courtesy of a one-man wolf pack, a bizarre yet effective Mike Tyson cameo, and a baby jacking its little weenus.

Phillips' comedic mystery—about three groomsmen trying to locate the groom after a night of hard partying in Las Vegas—used its detective story veneer and subversive unpredictability to show that a high concept is more important than big-name stars. It also doesn't hurt to have Zach Galifianakis on board to drop quotable after quotable, or a manic Ken Jeong as your villain.