As stated in the title: is an arrow, bolt, or other object that is generally used as ammunition, count as a weapon when determining bonus effects from other feats/abilities? For example:
Dreadful Strikes - 1d4 psychic damage - TCoE, pg. 58
When you hit a creature with a weapon, you can deal an extra 1d4 psychic damage to the target, which can take this extra damage only once per turn.
It seems clear that hitting a creature with a sword via melee, or even a thrown weapon, like a dart or dagger, would benefit from this feature. But since Arrows and Bolts are “considered” ammunition, they would not (unless used in some other improvised way).