I've only played 1st and 2nd edition, but I'll give this a shot.
Aquarius = water. So I'd say a magic trident, like Poseidon uses.
Pisces = fish. How about a magic net? Throw it at an opponent at a +whatever bonus and they are immobilized for x rounds or whenever you utter the magic word.
Aries = Ram. A big powerful sword. Can't have a set of magic weapons without a sword. Make it two handed.
Taurus = Bull. A mace. A powerful mace with a huge damage bonus.
Gemini = Twins. Two throwing axes. If you wield both simultaneously, you get a significant to hit bonus.
Cancer = Crab. Crabs have pincers. How about a magic mancatcher?
Leo = lion. I'm thinking a lion figurine. Say the magic word and it turns into a real life lion, faithful to the caster and with a very thick hide. Sorta like that lion Hercules had to fight.
Virgo = Virgin. Something that protects the wielder from attack. Let's say a magic shield with an extra AC bonus against any sort of thrusting attack.
Libra = Balance. Hmmm. How about a suit of magic armor that prevents the wearer from falling down?
Scorpio = Scorpion. Scorpions are poisonous. A dagger that, when wielded by a thief or assassin, will cause the victim to save vs. poison or die.
Sagittarius = Archer. A magic bow of course.
Capricorn = Goat. What do goat herders use? Staffs. A magic staff!
(That would be my first draft in my campaign. I'd probably make one or two adjustments after some thought, but it should serve as a starting point.)