speak for yourself
Waiter：Would you like to have some pizza?
Jerry: No one wants pizza this time.
You：Speak fo yourself！I'll have a cheese pizza with tomatoes and mushrooms on it.
speak for itself
I think my work these past few months speaks for itself and makes me more than qualified for this position.
I'm sorry I can't hear you. Speak up, please!
speak one's mind
Can I just speak my mind, even though you probably won't like what I have to say?