Intended User: Most anyone,outdoors best.  
Advantage:  Very Cheap and Easy
Disadvantage:  

Courtesy of Justin G.

This one's a simple one; it's a hanging pell.  If you take a plastic laundry basket (one of the cheap bouncy ones) and cut the rim and bottom off, you can roll it into a tube about the size of a torso.  Then get three PVC pipes, one long enough to reach one armspan, and the others long enough to be legs.  Stick the arm-length one through holes cut in the basket so that it is horizontal at the top, like outstretched arms.  Then place the legs in the bottom diagonally, so that they stick out like legs.  They can be
secured with tape or rope or whatever seems fit.  Then the whole thing can be covered with some sort of old clothing or something if desired. I don't recall what I suggested for the head; I think it might have been a soft
sport ball.  Anyway, the advantages of this pell is that, besides being cheap, it takes less work/effort to make than the concrete one, and is easier to move.  The torso is also much springier than wood, or even tire, so that a hit, rather than just bouncing off, actually makes an impact.  It
is also a little bit more realistic than a post; the legs can be left out, if desired.

Parts List: 
3 pieces of PVC about 36" long

1 plastic laundry basket

Duct tape, clothing and rope as reqired.

Ball for a head.