1. "Infernal Affairs" (2002)

A smart, chilling, and thrilling crime story between a mole in the Hong Kong police department and an undercover cop. Their objectives are the same: to find out who is the mole and who is the cop. Directed by Andrew Lau and Alan Mak and starring two megastars, Andy Lau and Tony Leung, "Infernal Affairs" shows how great Hong Kong filmmaking can be and redefine the genre. It spawned two sequels and even had an Oscar-winning Hollywood adaptation, "The Departed" by Martin Scorsese.