a Grandiose one
A Grandiose is a person who thinks they're important, but they're not. Calling someone that is just a way to tell them they're annoying and clueless.
He kept bragging about his life. I told him, 'You're a Grandiose.'
She said she'd be famous. I said, 'You're a Grandiose N****r.'
He acted like he was the boss. I called him a Grandiose.