I'd say as of now it's:
1. Murray
2. Federer / Djokovic
4. Nadal
...
5. Tsonga
6. Berdych
If Murray repeats his 2012 form I would favor him against anyone probably. It would be interesting to see how he fares against Nadal now, if Nadal manages to survive the 1st week and eventually get to him.
Djokovic and Federer are about even me thinks, with Djokovic being the more solidy and less streaky of the two. Federer has a bit of a greater chance to be upset early if we go by the last few years, but if he finds his form through the tournament he has a very good chance to win as always.
As for Nadal, he will enter the tournament with a confidence boost after his latest FO win as usual, but again, so was he last year after probably his best FO campaign and he got Rosoled in the 2nd round.
Its been almost two years since he made a final there too. But well, there will be no other two times Wimbledon champion on the draw, so he may surprise us yet again.
Then there is a good gap after the big favorites, followed by Tsonga and Berdych. Tsonga would be my outside pick. His game can really click on the grass. The question is whether he can go through at least two big favorites. After Tsonga there is the streaky Berdych, who has the game to go deep at SW19.
My dark horse pick this year will be Grigor Dimitrov. His game is maturing and as a Wimbledon Juniors champion, he also has the grass pedigree to go deep and perhaps cause some surprises.