Football. American that is, Ive never played aussie ball so I wouldn't know what that's like but from my point of view football is, Its the most physically demanding and hard hitting sport there is. For me at a Quarterbacks position its the most mentally demanding as well, Plus getting pounded into the ground by a 280+ pound lineman hurts like HELL. Or getting blasted by a 250lb linebacker at full speed from the back is quite excruciating too. Ive played baseball, softball, basketball soccer, Golf and several other "sports" that I don't consider them to be and football takes the cake.