An onsetter.
A hitchhiker.
Someone who passes, someone who makes a pass.
A passed pawn.
One who is able to "pass", or be accepted as a member of a race, sex or other group to which society would not otherwise regard them as belonging.
One who passes something along; a distributor.
One who succeeds in passing a test, etc.
A football player who makes a forward pass, who may be (but not limited to) the quarterback.