Half-orcs are already as good as WF's (slightly better in fact) damage wise even without using a favored weapon (two handed). Giving them a two handed weapon would really put them over the top damage wise....although that might not be a bad thing mind you.
To be honest a Half-orc should have a melee style weapon like a spear or axe...that is their prefered weapon type. Axes would proably make the most sense.....and since they favor two handed weapons...a great axe makes the most sense but that would be extremely over powered especially in the early levels.
Not that many two handed weapon choices left though. Great club is worthless and the H-orc would be better using a different 2 handed weapon again instead, maul doesn't make any sense and neither does quarterstaff (although the Q-staff is actually BETTER then the great club heh). A great sword is already taken and also doesn't make that much sense so honestly unless you give them great axe there is no way to really give a H-orc a two handed weapon that makes sense.....and isn't overpowered.
The other option though is to give EVERYONE a two handed weapon choice...which means it doesn't have to make sense only for the H-orc. A Q-staff choice for everyone does make sense for instance...and to a lesser degree Maul also makes sense. With Ratkillers though that also could be considered overpowered to some degree so shrug.