Came across an interesting wikipedia entry about the 'snark mark' quite by accident and thought the MGoBlog community could benefit from it. Also referenced in the article: doubt point, certitude point, acclamation point, authority point, indignation point, love point, and the intriguingly named, Interrobang(). Surprised a grammar geek hasn't pointed it out here yet though, I guess one's doing it now.
As we all know, irony and sarcasm can be difficult (at best) to detect over written communication. The mark is supposed to be a backward question mark. Alas, even as I write this post I cannot even ctrl+c & ctrl+v such punctuation. Supposedly a 'bracketed' exclamation point -(!)- or question mark -(?)- work in lieu of the real deal, depending on the type of statement being punctuated.
I spent 30 seconds brainstorming a way to try and market this but concluded that you probably have to be Apple to pull it off and even then they'd have to make it a "we're cooler than PCs" marketing meme. I certainly wouldn't buy a new keyboard for half of a key.