I'm just talking visuals, not power creep.
Ranger -- Have the different ranger races be able to tame pets unique to the race.
Necromancer -- summoned minions take a different form given the necromancer's race: sylvari - leafy, root-like minions; Asura - mechanical golems; Norn - beasts of the north; ... etc.
Those are the two that easily come to mind.
I see no difference playing a Norn/Charr/Asura/Human MM Necro.
"That's what" -- She