Nah gammon
A loud way to say you're not going to do something, like you're trying to shock people with how bad you are at life.
Nah gammon, I’m not going to the party. (He showed up in a clown costume.)
Nah gammon, I’m not doing my homework. (He failed the test.)
Nah gammon, I’m not talking to you. (He texted you 10 times.)