Primarch Leman Russ of the Space Wolves - The Emperor travelled to Fenris Russ refused to pay him homage, going as far as challenging him. He won 2 of 3 parts (eating, drinking) but lost to the Emperor in fist-fighting. Having at first seemed like a disappointment, a drunkard and a boaster, the Primarch suddenly launched a furious attack. This very challenge proved to the Emperor that this was indeed one of his sons.
Warhammer 40k - "The Emperor of Mankind in full battle armor regalia." "You see this icon of the Emperor, if I someone gets blood, greese, or a finger print on it so help me I will drive this ship into the eye and drop whoever damaged my holy icon off the plank, I HAVE THAT POWER!"