One who tags themselves on other people's posted photos on facebook. Even worse, a person who tags themselves on their own uploaded photos thus thinking the high number of tagged photos on their profile makes them look cooler... even though it could not be further from the truth. It is mostly done by bros with generic names and very insecure girls who are usually way too tan.
the tag in the collar of a shirt when it is exposed above the collar. common courtesy requires one who sees a tagflag to inform the wearer of the shirt with said tagflag.
The ugly/fat girl that is usually found tagging along behind a good-looking girl. Never normally fit in and tend to be the loudest. They think that shouting makes you beautiful.