Just had the funniest end to a game I've ever had in the short time I've been playing:
Mirror match, tempo mage. He's got 1 health left, I have 7. He's got a Mad Scientist, Spider Tank and one other five-attack minion. I've got a Mad Scientist, a barely-alive Water Elemental and two 0/2 taunts from playing Mirror Image.
It's his turn, and he Flamecannon's one of my taunts. All he has to do is kill my other taunt with his Scientist, then hit my face with his Spider Tank and other minion and I'm dead. Instead, he gets cute: He kills my taunt with his Scientist, uses his Tank and other minion to kill my Scientist and other minion to clear my board, then plays Rag so that, upon the end of his turn, it'll hit my face (the only remaining target) for 8 and kill me.
However, when he killed my Scientist, it activated Mirror Image. He plays Rag, and my secret spawns a Rag of my own. He ends his turn, his Rag hits mine instead of my face, and I use my hero power to kill him. So damn satisfying.