The Peacemaker (1997)
In this political action movie Clooney plays Thomas Devoe, the lead character opposite Nicole Kidman's Julia Kelly.
I don't think this was a very popular movie and didn't make very much money but I think it was a great film.
O Brother Where Art Thou? (2000)
One of my favorite films of all time, Clooney plays one of the lead characters, Ulysses Everett McGill along with Tim Blake Nelson and John Turturro.
This Coen brothers movie was supposedly loosely based on Homer's Odyssey and is set during the Great Depression.
Clooney won a Golden Globe Award for Best Actor in a Motion Picture Musical or Comedy.
Oceans Eleven (2001)
I really enjoyed this movie and it is kind of strange that I have yet to watch either of the sequels.
Clooney plays Danny Ocean in this re-make of a 1960 films of the same name.
This movie had an amazing cast which included Brad Pitt, Bernie Mac, Don Cheadle, Carl Reiner, Matt Damon, Andy Garcia, Julia Roberts, and Elliot Gould, among others.