10. “Big Fat Liar” (2002)
Who Giamatti plays: Marty Wolf, an egotistical and greedy movie producer who accidentally hits teenage compulsive liar Jason (Frankie Muniz) with his limousine. When Jason leaves behind his creative writing assignment in the car, Marty takes it and plagiarizes the story into a blockbuster film, prompting Jason to travel to Hollywood and seek revenge.
Why he’s great: Yes, “Big Fat Liar” is a very silly movie. But that doesn’t change the fact that Giamatti is genuinely, unironically great as the pompous dirtbag Marty. He leans fully into the role’s unlikability, practically sneering with every line. What makes his performance great is the physical comedy chops he gets to demonstrate when Jason’s revenge scheme begins, as he endures horrific pain throughout the various pranks and jokes he’s made the victim/butt of, and very appropriately hams it all the way up. You’re both cheering for the blowhard to get his comeuppance, and feel a bit bad when it actually happens.