Hi,
In that case, it's not a characteristic or an option that you should use.
You want to create a custom field of the table "item" via the menu Display>Custom fields (Business edition only) and in the custom field, you can enter a "select" value as first choice with an empty value field and make the field as required so that it will behave exactly like you're describing.
I didn't understand your question regarding the "select value". Could you describe more precisely what you want to do ? Maybe with some screenshots ?