In the SI - the current metric system - that would be the kilogram. In older metric systems, the gram has been used as the unit of mass.
You would measure that in grams, or milligrams.
Kilograms are the standard unit of mass in the metric system. Therefore, grams or milligrams can be used to get the mass of smaller objects.
I would use grams.
The kilogram would be logical.
The metric unit of mass is the kilogram. Why you would need to measure the mass of a necktie is beyond me.
you would use gallons