Regarding the guardian path ability Sacrificial Shield, what counts as a weapon attack?
Clearly getting hit with a sword does, but what about a touch attack spell or a dragon's breath weapon?
An attack that's made with a manufactured or natural weapon, or an unarmed strike.
The Fighter Weapon Groups are a good list as to what you can expect from weapons that you can make attacks with (hence a weapon attack). As for Touch Attacks, ask your GM as to how he would run it. Personally, I would allow Melee Touch Attacks to be deflected, but not Ranged Touch Attacks.