The hand-shake refusal. In the heat of the moment, whatever the circumstances, is it right not to shake hands if a match was played fairly? Probably hurt like hell getting hit by Almagro's drive but it happens if players are aggressive and the receiver is not quick enough to defend.
Big talented boy lost his cool and still managed to win a really tight one (that's interesting actually). File this one under not appropriate.
Are there circumstances where a hand-shake refusal is appropriate however? Multiple blatantly bad calls, using purposeful distracting behavior?