is there a good weapon i can make using copper bars? Terraria

Answer 1

No, since practically you can't make any decent weapons from Copper bars.

I would recommend making armor for yourself with it until you find better gear.

I would aim to get gold ore first once you reach gold tools and armor you will be ready for the bigger leagues

(gold armor is required to make Molten Armor)

(silver armor is required to make Jungle Armor)

Answer 2

You can make a copper broadsword which swings around when you use it; a shortsword which lashes out in front of you very fast (I consider it uesless); and a bow which can do 8 damage with arrows.

 

http://terraria.wikia.com/wiki/Crafting