Expressing surprise:
That’s a surprise.
Wow! What a surprise!
This is such a nice surprise.
I must say it surprises me.
I’m completely surprised.
That’s very surprising!
I find that very surprising.
How very surprising.
I find it extraordinary.
That’s incredible!
It’s unbelievable.
Wow, man! That’s awesome.
Really?
Oh my gosh / Oh my God.
My goodness.
I had no idea.
I never expected it.
I didn't have a clue about this.
Expressing disbelief:
You’re kidding! / No kidding! / Are you kidding?
You’re joking! / You must be joking!
You’re not serious. / Are you serious?
I don’t believe it.
I don’t believe a word of it.
I can’t believe it.
That’s hard to believe.
I find it hard to believe.
I can’t believe my ears.
I can’t believe my eyes.
You don’t believe it. Do you?
Seeing is believing.
It can’t be true.
Oh no! That’s not true.
I don’t trust you.
That’s impossible.
Oh, really?
Is that so?
I don’t think so.
I can’t think of it.
You don’t say.
Oh, come on!
Don’t make me laugh.