Exactly/Absolutely correct./You're telling me.
You can say that again.
You took the words right out of my mouth.
You're talking my language.
You said it.
I couldn't agree with you more. /I agree with you 100 percent.
We agree on everything./we see eye to eye on most things.
I agree./I'm with you./You're absolutely right.
I'm all for it./Good suggestions./I'm in favor of it. /I'll back you up on this one.
You hit the nail on the head.
A: Mom told me to buy you anything you wanted with the money she gave me.
B: I think we should buy all these candy bars.
A: We can't do that. Choose one. I like this one, it's crunchy.
B: I never had that one before.
A: Try it. I bet you like it.
B: This is really good, you're right.
A: I told you so.
B: You're such a smart older brother, you know so much.
A: You got that right.