I read online about many home made pinatas from brown paper bags, and my older brother made one from a gift bag for my niece's birthday....but I wanted something round.You know, I wanted to smash the bad guy, a pig! I would have made paper mache, but I didn't have the time(which seems to be my life story haha). I found my solution at work, and they even gave it to me for free from the window display: A Green paper lantern. They were originally from Hobby Lobby in a 3 pack of lime green lanterns costing $5.99-7.99. I used the big one as the pinata, and the small one as a decorative "play" pig (which I never got a picture of finished, but I just added a paper face!).
Because they have a waxy/wire body, I figured it would be pretty sturdy overall, but the paper is so delicate I reinforced it by gluing it sheets of newspaper to the inside (including 3 in the bottom where the hole was). It became very sturdy very fast! I didn't even use the metal wire support in the middle. 
To give it a "Pinata" look, I bought a roll of Crepe Paper Streamers ($0.97), cut the crepe paper about 3/4th of the way through and then ran a strip of glue along the part I didn't cut, attaching it to the lantern.
I made the eyes and nose out of printer card stock and outlined them with sharpie, attaching them with tape.
*****A Tip to Anyone making this: REINFORCE THE TOP 5 inches or so with packaging or duct tape, ours kept it's shape for many beatings but it felt down on the first hit! I think we also had too much candy in it weighing it down. More layers of newspaper (think inner "paper mache") would help as well. I did NOT use the wire that supports the middle as I said, I thought it might be dangerous for hitting. The newspaper was enough reinforcement to keep it circular. The very thin waxy wire that circles the lantern from top to bottom didn't pop out or break at all, it was like this neat piece of dental floss that helped rip the pinata apart =) .
