In addition to the above, there are quite a few actors I admire. In many cases, I know almost nothing about their personal lives, and so I don't know whether they're admirable in all respects, but I admire their work.

Ben Kingsley (I just saw "House of Sand and Fog." Brilliant!)
Ian McKellan
Robert Duvall
Bill Murray
John Cleese
Robin Williams
Robert de Niro
Harvey Keitel
Jeff Bridges
Dustin Hoffman
Meryl Streep
Kathy Bates
Jack Nicholson
Susan Sarandon
Tim Robbins
Sean Penn