I'd say

final say

The right to make a final decision.

have a say

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

I'd like to see someone try

Expressing a threat or challenge to someone.

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.

needless to say

Clearly, obviously.

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).