When you think of combat sports, you cast your mind to Pro Wrestling, Boxing or even Kick Boxing. As demanding as all those sports are (hey, listen WWE was the gospel truth when we were all kids) they all pale in comparison to the Ultimate Fighting Championship. Fighters in the UFC, some of whom are former Olympic wrestlers, are usually trained in boxing, jiu-jitsu, Sambo, wrestling, Muay Thai, karate and judo, to name a few. They're basically the reason Mixed Martial Arts came into being. And while they've revolutionised what fighting means, they've also redefined the K.O. Yeah, the knock-out! In the UFC, knock-outs are unbelievably brutal. Here are the top 10 in UFC history. Caution: These knock-outs are unbelievably brutal and not for the faint hearted.