needless to say

final say

The right to make a final decision.

have a say

To (receive the opportunity to) voice one's opinion.

I'd say

It is my estimate or opinion.

I'll say

Used to indicate emphatic agreement

let's not and say we did

Indicates that the speaker does not agree with a proposed action, and does not wish to participate.

say again

"What did you say?" or "Repeat what you have said." A polite formula used when one has not heard or understood what has been said.

say cheese

To smile for a photograph by saying the word "cheese" (the vowel of which, when pronounced as is usual in English, forces a somewhat smile-shaped mouth).

say goodbye

To separate from someone or something.