So what? Who cares? Expresses disinterest, disregard or lack of concern.
Used to express astonishment, shock, incredulity, or disbelief (as a shortened form of expressions such as "What the fuck is going on?", "...are you doing?", "…is this?" "…is it" or "...is that?").
Used to express nonchalance or the dismissal of any consequences of something one is about to do.
An intensive form of what.