I was thinking a younger
Harrison Ford would be a good Faramir, if he was an unknown. Sounds really bizarre, but think about it.
Also
Jeremy Irons as Grima would be closer the image of him in my head.
Ian McKellen would have made a wonderful Denethor.
And for some reason I keep seeing
Michael Palin as Bilbo!
EDIT: One more.
Kathleen Beller as Arwen.