Me too. I want Predator 2 (1990) guests like Gary Busey and Bill Paxton too!
Apparently Adam was nearly in AvP-R (2007) reprising his role from Predator 2 but couldnt do it due to scheduling conflicts.
I read that recently and I have seen Predator 2 a good few times and totally can't think who he is! I don't mind Firefly but I would absolutely, positively meet him for Chuck! Everything he does in that just has me in stitches.
In Predator 2 Adam plays one of the Feds - the one who didn't go into the warehouse but monitored things in their wee van. At the end he got out of the helicopter and raged a bit at Danny Glover's character that they "almost had him".