I'll start by saying that I'm kinda sick of seeing Knightly in the hot/tough-chick role. That said, I did like her in PotC. Her teeth bug me.
Casting the whole trilogy, eh? I do like some of the above choices but the ages for many of them are WAY off. Sure, they could change things around but I'll keep my cast as close to the novels as possible. So...
Slicey D(o' Urden) is a tough one. And since he's not really considered the main character that makes it even harder (he was originally a sidekick to Wulfgar). Especially for the look. I really like the choice of
Samuel Le Bihan as Drizzt Do'Urden based off of his character in Brotherhood of the Wolf. I went to see that with my gaming group and there were little manly squeals of, "OMG, it's Drizzt! TWO swords!" >ahem< And I *really* can't think of anyone else who could looks the part and can pull of some of the physical stuff.
Since we're on BotW, I'd like to see...
Vincent Cassel as Entreri. Right build and attitude. Can pull off eeeeevil, non-caring and assassin in his sleep.
Wulfgar - If Vin Diesel or The Rock had a more nordic look I'd be cool with either of them. Vin would be the better choice because of the voice and he looks pretty young. Not as young as he needs to be I can't think of a single actor that big that looks like he's in his late teens. Except for maybe...
Tom Welling as Wulfgar. Seriously. He's big (6'3") and has some acting chops. Just needs to deepen the voice a bit and bulk up a bit.
Bruenor - I have no idea. Take any of the good character actors from Braveheart or Gladiator who can do an accent (or have one naturally) and act all gruff and fatherly.
And since we are making large Scottish men look less than 4 feet tall using computers how about -
Zach Braff as Regis. Can play laid back, funny and courageous if he has to. I'd also not be opposed to Dave Foley.
The easy to cast - The actor has to be good-looking and be able to at least look good holding a pair of scimitars. And the trademark "pissed off" look has to work as well. With those traits in mind I'd go with eith Ewan McGregor or
Catti-Brie - Again, not too hard as the character isn't terribly deep. The only requisite is being able to do the accent and look good holding/firing a bow.

I like the above pick of Scarlett Johansson. But it's all about the natural red hair so lets go with
Christina Hendricks as Catti-Brie - Saffron from Firefly.
Nicole Kidman as Lady Alustriel. She's got the look and the screen presence.
Akar Kessel - I like Paul Giamatti here. But I'd be okay with David Hyde Pierce, playing off-type.
