*twitch twitch*
Which authors, I think.
Which. I might be wrong, but it pleases me better.
But either way, it's an excellent question and I'm really struggling to answer it.
The reality is that there are obviously
loads, but it's one of those times where I'm um-ming and ah-ing and then seeing someone else mention a name and going "Yes! Him/her! Of course!"
In terms of nailing the truth of the everyday, the mundanity, the casual throwaway nature of speech, though...SK's possibly close to matchless. That's not to say some things don't clunk, it's just that he seems to produce fewer instances of it. (While some otherwise very good/excellent writers couldn't write convincing dialogue or 'do' character motivation if their lives depended on it.)