"Hey, what are you waiting for?"

• "Are you serious?"
• "You've gotta be kidding!"
• Repeated word in Def Leppard & Sheryl Crow song titles
• 'Be a sport'
• "You are so obviously lying to me"
• "Let's move it!"
• "Let's roll!"
• "Get the lead out!"
• "Time's a-wastin', let's go!"

Wiktionary Word definitions in Wiktionary
contraction (alternative spelling of c'mon English)