Crowdbreaker

Someone (usually big or tall) that you follow through a large crowd of people. They "break" the throng of people, leaving a large space behind them for potential following.

Bob: Man, it's gonna take forever to get through here. Look at all the peeps.
Fred: Quick, find a crowdbreaker.

Tall Guy: Hey, let's go over there!
Short Guy: K, you be our crowdbreaker.