I don't even know who the player is, but I would want the best pass rusher in the NFL. Everything else is fixable, IMO, or can be covered for with a dominant guy that offensive lines have to account for x2 on every play.
I'll take someone at a position which is hardest to find - shut down corner or true 3-4 outside linebacker. Age, durability, character etc all come into it. I really can't think of anyone better then Demarcus Ware or Darrell Revis. Ware can beat any tackle in the league and Revis can shut down any wide receiver. They would change the way we would play defence. Offences would have to account for them on every play and they would raise the play of others.