Ok so I just want to point out that in 3.5 there was a feat called monkey grip in one of the complete books, probably warrior, that allowed you to wield a two-handed weapon in one hand with a -2 penalty. 3.5 is extremely limiting so the fact that 3.5 allowed it to happen surprises me that pathfinder hasn't come up with a feat for it. Perhaps this would unbalance the game when including pathfinders other modifications to the feat selection. Anyways my point is that it can be done. I have been in real life fights where I have used something that I could easily wield in two hands but used it only in one hand by pressing the weapon against my hip and swinging it with my hand. Effectively my hand is applying force to the weapon to force it to go a direction and my body is preventing the bottom part of the weapon from moving with the top part. I could easily see this being applied to a big spear or axe. In some games you have to have a certain strength score in order to do it and still take some sort of penalty. My point is realistically it can be done but pathfinder has created no window for this to happen. Now weapons that are made for giants are a different story as those things might be the size of a person and therefore just too unwieldy.
Well so barbarians can do it. So does that mean I am a barbarian in real life?