Bah, you forgot Tom Arnold! Say all you will about most of his other work and his personal life, but he's consistently funny here and his exchanges with Schwarzenegger are great.
And Bill Paxton rocks in his role. That had to be so much fun for him.
Yeah, Cameron was planning one for ages but basically shelved it after 9/11, saying he didn't think he could have fun in the world of terrorism again, or that it'd be appropriate.