Can you also accept "Let's get some runs!" for Harry Caray's catchphrase? He yelled it after every game after "Take Me Out to the Ball Game." That was the first thing I thought of. The guest singers at Wrigley still do it.
Technically you're only supposed to yell it when the Cubs are losing. It's trademark Harry Carey, but he started doing the 7th inning stretch and "let's get some runs" when he was the White Sox announcer, so although it's identified with the Cubs now it wasn't always theirs.