Watched Coffin Rock earlier today, and it really reminded me of how shamelessly underrated Australian actor Robert Taylor is, internationally anyway. He has such range and onscreen charisma, such variety in expression. I wish he got more internationally acknowledged and distributed roles, because he's fan-frakking-tastic, one of my all-time favorite actors.
David Wenham is another Australian actor who really doesn't get enough credit for his work. I'm not a particularly emotional person, especially when watching something as superficial in a way as a film, but his portrayal of Faramir in Lord of the Rings: The Return of the King continues to be the one and only performance ever to have almost made me weep in a movie theater (and I gotta tell ya', it was close. I even let out a sound).
I also want to bring up Owen Wilson, who has far wider range than the comedic prankster or sidekick he's always typecast as, and Val Kilmer, who has been my all-time number one actor since I was nine years old. Finally, I def. agree with Northern Star ^, bringing up Parker Posey and Maria Bello.