Ok. Am in a debate with friend about whether Thanks! and No Thanks! require an exclamation mark or not. I assumed they always have them, but she assumes it makes it sarcastic (especially in the negative No Thanks!). I automatically put one in when I write in a text message eg. Thanks for coming over! So, who is right? (I know, I know, overuse of exclamations is not good form, but I do love 'em).