Last night I saw the movie and a question has been bugging me since then. I came back at 2 in the morning and looked up IMdB, but that was no help.
Towards the end of the movie when Tom Cruise is looking for a guy named Crow(who he was supposed to kill) he come into a hotel and threatens the desk clerk with a gun when the desk clerk refuses to give Tom’s character come info. Who is the desk clerk? I am fairly certain that it is some rock star. He has a salt and pepper head of hair and a small Van Dykish beard.
My doubts were strengthened by the fact that IMdB lists Cameron Crowe and Cameron Diaz amongst the uncredited bit players.