From the top of my head I would pick Christain, but I think Triple H will win it, especially if he hasn't comeback by then. I think it'll be a surprise like when Edge and Cena won it. Not sure if Christian is healthy enough to return yet.
It seems that the WWE prefers multi-year veterans to win the Rumble based on the results for the past few years, so if that is still the case this time around, Christian and Punk are the most viable. Either way, I'll be damn happy.