I think the best and most direct translation is: 'you scared me to death!' As below: 吓死我了，我还以为我说错话了呢。 You scared me to death, I thought I said something wrong!! 吓死我了，你以后别突然在后面拍我 You scared me to death, next time dont surprise me from behind!! What Linda said souds OK for this: 你个死变态 you freak! 你白痴吧你 you idiot!

吓死我了，我还以为我说错话了呢。Thank God I didn't say the wrong thing. 吓死我了，你以后别突然在后面拍我 You scare me! Don't suddenly pat on my back like that again. 你个死变态 you freak! 你白痴吧你 you idiot!

interesting topic: Maybe not quite suitable for your example, but is "scare the bejesus out of sb." one ? :)

我想你應該是想問英文該怎麼說吧. You freaked me out. 另外一個我覺得不錯可以分享的(電影裡聽到的)： You take my breath away 不完全一樣,但是很生動的