After Joffrey was poisoned at his own wedding (well played, poisoner), Tyrion was put on trial for his murder, even though he clearly didn't do it. Tyrion took the whole thing in stride*
(*okay, so it didn't look exactly like this on the show)
until Shae betrayed him and he ran out of f**ks to give. Tyrion demanded a trial by combat in one of the best scenes
in the whole show so far. His champion, the supremely sexy Prince Oberyn Martell of Dorne very nearly won that trial, but got a little too cocky and ended up with is head smashed like a grape (not pictured because nobody needs to re-live that). At least he managed to mortally wound the other guy in the process.