Guild Wars 2

I suggested it for LotRO and i’ll suggest it here.
The ability to change hairstyles via an npc would be awesome.
Additionally due to how ArenaNet have fantastically done this game (implementation wise) you would be able to add new hair cuts for each race and actually have someone shouting about it via a town crier or something.
The Sylvari could have a gardener visit them in the grove to trim their “hair”.

While on the subject of altering looks.
Maybe implementing a gym to change the physical build of your character. Not the height, just build. This would give players the ability to define how they want their character to look in the armour they earned.

lol at sylvari option