Note: I am aware that I am quoting from 3rd party materials, and not core Pathfinder stuff.
A soulknife must choose the form of her mind blade at 1st level. She can either form it into a light weapon, a one-handed weapon, or a two-handed weapon. Once chosen, her mind blade stays in this form every time the soulknife forms her mind blade. The light weapon deals 1d6 points of damage, the one-handed weapon deals 1d8 points of damage, and the two-handed weapon deals 2d6 points of damage. All damages are based on a Medium-sized creature wielding Medium-sized weapons; adjust the weapon damage as appropriate for different sized weapons. In all forms, the mind blade has a critical range of 19-20/x2. A soulknife with powerful build or any similar ability forms an appropriately-sized mind blade dealing the size-appropriate amount of damage.
Emphasis mine. The Half-Giant's Powerful Build trait reads as follows:
Powerful Build: The physical stature of half-giants lets them function in many ways as if they were one size category larger. Whenever a half-giant is subject to a size modifier or special size modifier for a Combat Maneuver Bonus or Combat Maneuver Defense (such as during grapple checks, bull rush attempts, and trip attempts), the half-giant is treated as one size larger if doing so is advantageous to him. A half-giant is also considered to be one size larger when determining whether a creature's special attacks based on size (such as grab or swallow whole) can affect him. A half-giant can use weapons designed for a creature one size larger without penalty. However, his space and reach remain those of a creature of his actual size. The benefts of this racial trait stack with the effects of powers, abilities, and spells that change the subject's size category.
Again, emphasis mine. Does this mean that a Half-Giant can create Large mind blades because they can use them and are therefore appropriately-sized (and the rules for the Mind Blade say this because it doesn't say medium-sized only), or does it mean that they can only use Medium sized Mind Blades? From what I can tell, the difference in damage for a two-handed weapon would be 2d6 VS 3d6.