What does it imply when someone addresses someone else with the phrase “you of all people”?

Question

Consider a situation in which two individuals are talking — person A and person B. In the conversation, A addresses B with the phrase:

“you of all people”.

What does the phrase “you of all people” imply here, and what is its proper usage?

Answer 1

It's an idiom phrase: "of all people",

of all people
_idiom

— used to emphasize that a specified person is the person one most or least expects to do or know something
// You, of all people, should know the answer to this.
// My best friend, of all people, betrayed me.

(Merriam Webster)

used to show that you are especially surprised at a particular person's behaviour because it does not seem typical of them:

I thought that you, of all people, would believe me!

(Cambridge)

Note that it doesn't always have to be "people"; it can also be, say, "places" or "things".

Example sentences (from The Free Dictionary)

with "people":

• Really, Jeff, you of all people should know that it is never OK to get behind the wheel after drinking.

• And then Tom Hanks, of all people, stopped by to take pictures with our wedding party in the park.

with "places":

• If it's a rest they need, then why go to New York of all places?

• My parents are taking us to Louisiana, of all places. What the heck is there to do in Louisiana?

with "things":

• When he retired, he took up painting, of all things. He had never even picked up a paintbrush before that!

• After spending his childhood in and out of detention centers, he became, of all things, a cop.