I had a hard time believing the Muster-Agassi feud was over a pat on the cheek and ruffling of the hair but I'll be damned if what started out a cordial meeting at the net ended with a death stare from Agassi.
Seemed like an affectionate gesture on Muster's part but maybe he was trying to be disrespectful? Either way that's one of my all time favorite matches.
http://www.youtube.com/watch?v=ARAmugAt7GI