Heat and Lakers. They have the best players, and need the least amount of luck to win it all.
The C's have a decent chance, but they really need to stay incredibly healthy, since their strength lies in their depth and being able to throw player after player at the opposition.
And the Thunder...well, I still think they have arguably the most talent in the league, but they are so mismatched that the whole is less than the sum of the parts. So, they need to figure out that before they become a favorite IMO.