Henman against Roddick- TMC 2004
Safin against Federer- TMC 2004
Davydenko against Federer- RG 2007 (choked all three sets)
Yes, Davydenko was playing out of his mind all the way to losing all sets. Incredible match, this one takes the cake.
Also, alot of matches against Nadal on clay where opponent ends up losing in straights. Like Nadal-Andujar 2011 and Nadal-Almagro 2010.