Ayo

It is used to put emphasis on the sentence , with utmost feeling . It may or may not make you look cool. It can also be used to call someone and show surprise, disgust, happiness etc. just by adjusting your tone and expressions.

Ayo do you know what happened yesterday ?

Ayo I'm here bro.

Ayo you got to be kidding me.

Ayo you weren't suppose to snitch like that.

Did you really won the title? Ayo I'm so happy for you bro.