I found a light hammer recently that adds skill bonus to some non-combat skills. The question is, can a character not proficient in martial weapons emote using the hammer to obtain the skill bonuses?

Obviously a wizard can hold a hammer, even if he can't wield it effectively against a foe. I'm not sure how these magical enhancements are transferred to someone holding the hammer, though... Could he use a hammer to, for example, emote "building" something with the hammer, and obtain any appropriate skill bonuses for IC non-combat reasons?

The way weapons work, they won't grant any bonuses unless equipped. Thus, emoting something without equipping the item will not grant skill bonuses.

Also, while pretty much everyone can hold a weapon, the required feats represent a character's ability to wield/use it effectively. So, if you're a wizard with a hammer, chances are you're not going to be so hot building stuff with it, in the same way as you're no good fighting with it.

I do understand that the game mechanics prevent this - I am wondering for IC RP purposes.

Maybe this is a better example of what I'm asking:

Say the hammer granted +2 to charisma. Could a wizard pick up the hammer (even though he cannot equip it), tell a DM he has it, and try to roll a charisma check to influence a group of NPCs, and be granted the extra charisma modifier (not in the game engine, but in the DMs eyes)?

Or does he have to know how to fight with a hammer to gain the bonus?

Nope. 'Wielding' a weapon creates these bonuses (for instance, holding it by your side in a certain way that makes you look more impressive). For example CONAN wielding longsword versus RANDOM MOUSTACHE GUY wielding longsword. That's the way I see it anyway. You need to 'wield' the weapon, and properly, to get its bonuses, so you shouldn't really RP the stat. I'm pretty sure this'll never be a huge issue though, if someone allows you to do it, none of us are going to complain, just don't ask for a DM to give you a feat proficiency to do it from time to time harrr