can you cast magic weapon on a peasants fist?

Can you cast magic weapon on a peasants fist?

No: Unarmed strikes, natural weapons, and manufactured weapons are three different things. Being treated like a weapon is a big part of a monk/brawlers class ability.

Yes: Unarmed strike appears on the weapons chart as a light weapon and counts as one for purposes of effects that add to weapon damage rolls so its a weapon.

Nope you need Magic Fang. Unless said peasant had one level in monk.

Says so in the spell description.

MAGIC WEAPON

School transmutation; Level cleric 1, paladin 1, sorcerer/wizard 1
Casting Time 1 standard action
Components V, S, DF
Range touch
Target weapon touched
Duration 1 min./level
Saving Throw Will negates (harmless, object); Spell Resistance yes (harmless, object)
Magic weapon gives a weapon a +1 enhancement bonus on attack and damage rolls. An enhancement bonus does not stack with a masterwork weapon's +1 bonus on attack rolls.

You can't cast this spell on a natural weapon, such as an unarmed strike (instead, see magic fang). A monk's unarmed strike is considered a weapon, and thus it can be enhanced by this spell.

Linky

How about other weapon enhancing spells that don't call it out specifically?

I would argue that Improved Unarmed Strike is sufficient and the spell was written more specifically than intended but yes if you go exactly as as written magic weapon does not work on unarmed strike, even for clerics of Irori let alone peasants.

For other spells it would differ spell to spell depending on how the spells are phrased.

Basically there are three types of attack forms that I know of: Manufactured weapons, Unarmed strikes, and Natural attacks.

Most spells are specific to either Manufactured weapons or unarmed strikes and natural attacks.

If a spell simply says "weapon" it is my belief that it means Manufactured weapon.

Actually the need to include the exception in Magic Weapon for natural attacks and unarmed strikes suggests that weapon is any manufactured, natural weapon or unarmed strike.

Actually the need to include the exception in Magic Weapon for natural attacks and unarmed strikes suggests that weapon is any manufactured, natural weapon or unarmed strike.

Its not an exception, magic weapon calls it a natural attack.

(and then the bestiary universal monster rules says its not a natural atack)

If it just says "weapon", and not "manufactured weapon", it should be fine.

If a spell has explicit text referring to it's function on unarmed strikes, you follow appropriately.