Exactly/Absolutely correct./You're telling me. 

确实/完全正确/还用你说！（表示赞同）

You can say that again. 

你说的对。

You took the words right out of my mouth. 

你说出了我想说的话。

You're talking my language. 

我们的想法不谋而合。

You said it. 

你说对了。

I couldn't agree with you more. /I agree with you 100 percent. 

我完全赞同你的说法。

We agree on everything./we see eye to eye on most things. 

我们的所有意见都一致/我们大部分事情的意见一致。

I agree./I'm with you./You're absolutely right. 

我同意/我支持你/你完全正确

I'm all for it./Good suggestions./I'm in favor of it. /I'll back you up on this one. 

我完全支持/好建议/我支持它/这件事我完全支持你

You hit the nail on the head. 

你真是一针见血

Conversation:

A: Mom told me to buy you anything you wanted with the money she gave me.

妈妈给我钱，让我给你买任何你想要的东西。

B: I think we should buy all these candy bars. 

我想我们应该把这些糖果全买下。

A: We can't do that. Choose one. I like this one, it's crunchy. 

不行，选一块。我喜欢这块，是松脆的。

B: I never had that one before.

我以前从来没有吃过那样的。

A: Try it. I bet you like it. 

尝尝吧，我打赌你一定会喜欢她的。

B: This is really good, you're right.

真的非常好吃，你说得对。

A: I told you so.

我说过吧。

B: You're such a smart older brother, you know so much. 

你真是聪明的哥哥，你懂得真多。

A: You got that right. 

你说对了。