You can show sarcasm using '아주'. For example, "잘 한다, 아주 Good job!" and "내가 못 살아, 아주", this one is used when your friend forgot to do something or made a slight mistake(so you don't have/see what you wanted after all). Some sarcastic word/phrases are: 퍽이나 ; used to say what the speaker is saying will be unlikely to happen. 잘도 그러겠다 ; more mild than the above. 사돈남말하시네. means, "Look who is talking." 뻥치시네. means "You're full of hot air." 남이사. That's none of your business. 놀고 있네 / 웃기고 있네 / 웃기고 앉았네 / 웃기고 앉아있네 / 웃기고 자빠졌네 Funny 행복한 / 배부른 소리 하네 ; used to say the speaker is complaining about something ordinary people cannot affort to have/do. ㅇㅇ 좋아하시네 / ㅇㅇ 같은 소리 좋아하네 / ㅇㅇ 같은 소리 하고 있네 means, ㅇㅇ must be nice (example : A : 요즘 이게 유행이야. ㅡ B : 유행 같은 소리 하네.) 그렇게 살다 죽으라 그래. Tell him/her/them to live like that and die. It's used to say you don't care about their behavior or life style etc. If you use the honorific infix "시" with 반말, you sound sarcastic, like 뻥치시네.

Mostly, when you show your sarcasm, you say something normal with a sarcastic voice, just as in English. ex> 엄마, 나 우유 엎질렀어요!! -> 자~알 한다. I don't really remember other examples..

sarcasm = 빈정됨, 비꼼 ( I fould it in a dictionary) "Sarcasm back at you"= 너나 잘해 >>I've known new expression "sarcasm"