Watch out for Japan. I believe they will surprise many. Brazil in addition to be playing at home have a balanced team. I like their chances but hate the pressure that's on their shoulders. Speaking of pressure everyone is expecting much from Messi besides Argentina's weakness in defense. If Messi can perfect his free-kicks he will have a major impact on the outcome of WC.
I'm hopeful for Colombia. Spain is still a strong team but passing the ball around and no serious strikers will kill them this time around.
Argentina, Brazil, Colombia, Spain, Germany are my picks. Don't think Africa will do very well this time around. Iran & USA will have a good time at the beach or perhaps have a talk on peace in the middle east.
update: Classic final between Argentina and Germany