Shouted, (usually while interrupting someone mid-sentence), when you firmly believe you are right, period, regardless if you really are or not, and have run out of ways to argue your point. Also said as a means to shut the preverbial door in the other person's stupid face.
"Dude, I'm telling you, raisins are just dried grapes."
"Nuh-uh, they grow on trees, jerkface."
"Let me show you a gr-"