I would say BRB first, then agree with Jeremy about the carpet python. Yeah, GTPs and ETBs are beautiful and all, but they don't do much. I prefer active, moving (but not necessarily fast) snakes to the more motionless ones. And I've heard more stories of aggressive GTPs than of BRBs. My art teacher breeds BRBs and she swears by them.
I can't say for sure, since I've never personally owned any of the species listed, but I'll say BRB, carpet, GTP, corn.