If you actually threaten somebody that you will cause bodily harm while holding an instrument or weapon of some sort, it will likely be charged as an aggravated assault. Remember, the weapon could even be a rock in your hand. There have been plenty of aggravated assault convictions when a rock was used as a dangerous instrument. Those cases are not as good to prosecute, but they can be easier to defend. This could depend on the size or shape of the rock, and even whether or not the State actually kept the rock as evidence.
But weapons such as gun pieces, knives, sticks, and bats, can easily be considered dangerous instruments. In Arizona, offenses using dangerous instruments are very serious and should not be taken lightly. If someone is charged with a dangerous offense they should contact and experienced criminal defense attorney immediately.