I've met quite a few celebs at stage doors and various conventions/fan events and film premieres and feel lucky that I've not met anyone who could be considered "mean" (although I find Morgan Freeman's hands-off attitude toward fans disappointing...if you ever see him, don't expect more than a wave). But ones who really stood out as going the extra mile for fans:
I want to give gold stars to Winslet and Nicholson becase it was a December when I met Winslet and a January when I met Nicholson. It was absolutely freezing
but they still stayed outside signed autographs for ages.