ka-cha
The final slap in the face of any conversation. It's like throwing a punch and then spitting on the ground. You don't talk back after a 'ka-cha' or you're a sad excuse for a human.
Bro: 'So, what's up?' Me: 'Ka-cha.' Bro: 'What?' Me: 'You heard me.'
Girl: 'You're gonna text me back, right?' Me: 'Ka-cha.' Girl: 'You're dead to me.'
Mom: 'Did you eat your veggies?' Me: 'Ka-cha.' Mom: 'You're grounded.'