How to say "Oh my god" in Korean?

The expression oh my god is a good way to show your emotion. How about korean? yes it is same. There are several ways to mean Oh my god!
어머, 이런, 뭐야, 말도안되, 진짜?, 정말? 이럴수가, 대박

But! there are some slang as well. Those are really used often among teenagers.
뭥미, 헐,헉, 쩐다, 멘붕, 에바 and 레알?

They sound funny, don't they? They are informal words, whereas it would be much more enjoyable if you have fun with these kinds of languages.