我要给你个惊喜用英语怎么说

I will give you a surprise.

最标准的说法就是：
I will give you a surprise!
《变形金刚》里面父亲想给儿子买个车子，以示奖励。就说
I will give you surprise, son.

正规的说：I want to give you a pleasant surprise
口语化的说：I wanna give ya a pleasant surprise
倒过来说：You're gonna get a pleasant surprise
提问性的说：Would you like to have a pleasant surprise?

I have a surprise for you.

I will give you a surprise.

I will give you a surprise
比较简单但是实用