Im going to be slightly unfashionable and pick Randy Moss.
After re-watching a steady diet of '3 Games To Glory' over the last week or so, it became clear to me that our D has been greatly responsible for our recent success.
There were plenty of examples where we clearly out played teams for large percentages of the game, yet they were still hanging in there.
With addition of Moss (and Stallworth) I think it gives us a consistent quick strike ability on offense aswell as potent redzone weapons.
I really like the addition of AD and think he'll be an awesome asset this year, but BB has always managed to scheme his way round our intermittent shortcomings on defense (perennially injured DB corps for instance).
Im not one of those guys who is going to beat down on Gaffney/Caldwell - they did their best last year, but the credit for their improved performances goes to Tom Brady.
There is a reason these guys were available.
So, there, perhaps the one and only vote for Randy but I think he will be the guy who has the biggest impact on our offensive output this year, and therefore our ability to attack with our Defense.