Dublin Solo said:
Can't seem to find a suitable video for him, but I'd say Keith David. He's the one in "Pitch Black" playing the Imam, among other things. He does some voice acting in Mass Effects 2 and MW2.
And he's the one in the role of Goliath in "Gargoyles", for those who remember that show...
Jonathan Frakes also did voice-acting for Gargoyles (he voiced David Xanatos), and I think he's another good candidate, as is Marina Sirtis, who voiced Demona, on the same show.
I'd also like to suggest:
Michael Ironside (whom I didn't know was the voice of Sam Fisher)
Jason Statham (he voiced one of the NPC's in Red Faction 2)
Tim Curry (just an incredible voice. Period.)
Edit:
Michael Clark Duncan (again, just a great voice.)
Those are the ones that come to mind for me, but I certainly liked some of the other ones already suggested.