| KingHades |
Check out the Tekko-kagi-
http://www.d20pfsrd.com/equipment---final/weapons/weapon-descriptions/tekko -kagi
It specifically says that you can use this weapon defensively like a buckler. With that in mind, it seems totally legit that you could enchant it as you would a shield. I would apply the same rule to any weapon with the blocking quality. It's just that you would only get the enhancement bonus tacked on to your shield bonus if you were fighting defensively. Even then, the weapon would not be treated as a magic weapon for purposes of DR, etc. unless you then also enchanted it as a weapon.
It's odd conceptually, but it makes some sense to me. There's historical precedent for similar use of weapons when held in the off-hand, such as dual wielding with a rapier and main gauche.