I'm talking about that (potentially) massively powerful weapon found in Moldvay's treasure charts; the +1 sword, casts light on command (30' radius).
Bear with me a moment.
If you refer back to my RSA on the Light spell, you can see that the item effect is basically the same. Though it does list the effect as a 30' radius, not diameter like the spell. I'm not sure of that's a typo or deliberate change. Either way it's a fair interpretation that the sword is simply granting this spell-like ability to its wielder. So three things immediately come to mind here:
- The ability is on command, which means no limit per day.*
- Light can blind an opponent if cast on their eyes.
- It's still a magic sword that lets you hit things like wights and lycanthropes.
Following this model gives the user a huge leg up in a fight. Now, you could make the DM ruling that the light can only be centered on the blade as opposed to "targetable," and that would be fair enough, I suppose. Unfortunately there isn't a more detailed write-up of the weapon provided in the book. However, in Cook, there are a couple other weapons with spell like effects which do have some accompanying text. In those cases (charm person and locate objects), the powers are described as per the relevant spells. So that's a point for the original premise.
It's worth noting that even without the blinding ability, a light spell ability that doesn't take up a spell slot is a great resource for a low (Basic) level party.
* The Cook Expert items do include a frequency cap on invoking the powers, but they aren't uniform.