According to PHB you only have the attack action with your weapon. The once per rest special attack is an invention of Larian.
Some magic weapons may have special magic abilities though.
Limited arrows per rest is pointless as long as resting is not restricted at all.
In BG1+2 half of my inventory was filled with ammo and one of my priorities was to get a magic weapon with infinite ammo.
BG3 has no limited inventory slots and arrows have no weight, so that's pointless in BG3.
Prof. Dr. Dr. Mad S. Tist
World leading expert of artificial stupidity.
Because there are too many people who work on artificial intelligence already
