What weapon should Druid use?

Weapon damage also makes no difference. Your cat and bear form damage is based on a hidden feral weapon skill that is automatically set to maximum when you level up (5 times your level). You should use whatever weapon gives you the best stat increase (agility, strength, etc). This means that you do need to train to use each weapon type at the weapons trainers, but it is not too important to actually level up your weapon skill unless you are using Moonkin or Tree of Life form.