This is what im looking for, if youve played Warhammer Online you'll know that you can have a small health bar above your head which works nicely so you can see your health in combat quickly without taking your gaze away fom the combat.
Is there any addons that do that for WoW?
I havent found any yet, doesnt have to be all fancy just a small bar , text isnt required etc.
Actually the OP is talking about the HP bar above his own character's head, not other players/mobs. While you can enable Nameplates (that is what the feature in WoW is called) works for other players/NPCs, it will not show you a bar above your own character's head.
The closest one can get to that is use a HUD (Head's Up Display) that places bars on either side of your Character or to move your UnitFrame to an location that is easier to see.
Edit: The mod that p3lim just posted as I was posting this reply will also give a movable bar that you can place somewhere convenient.