In the recent issue of Chess Life a reader told this Walter Browne story. About 30 years ago Browne was giving a simultaneous in which the reader had one of the boards and a kid about 10 years old was sitting next to him. Late in the exhibition Browne arrived at the kid's board and made his move whereupon the kid told him he couldn't make that move because he was in check. Browne stared at the board then “with one majestic sweep of his hand sent the kid's pieces flying then moved on to the next board.” The writer told the nonplussed kid that he'd remember beating Walter Browne the rest of his life. I saw Browne a few times at tournaments and he always looked very nervous, like he was ready to blow a gasket, but really? Against a 10-year old kid? Why be such a snot?
Elizabeth Vicary, a US lady FM, once wrote an article where she said, “Chessplayers are very tolerant. I say this because so unbelievably many chessplayers have unbearably annoying board manners/habits/smell/loudness of breathing and/or compulsively vibrate the table with their legs, yet it seems like I’m the only person who ever says anything. Everybody else is a complete saint. I really do not know how they do it.” Read more on Ralph Ginsburg's article.
Are there no nice Grandmasters? These guys come to mind.
Edit: I forgot one...this guy: