¡No mames!

Mexican slang for no freaking way

A stronger, often more vulgar expression of disbelief or shock, akin to 'no freaking way' or 'you've got to be kidding' in English.

¡No mames! ¿Ganaste la lotería?

No freaking way! Did you win the lottery?

Ya, no mames güey, no fue para tanto.

Come on, dude, it wasn't that bad.

Dile a tu hermana que no mame, yo confiaba en ella.

Tell your sister that, what the hell, I trusted her.