Here's something that was cheap and easy to build. I took a Dollar Store Hallowe'en skull, repainted it, cut open the back, poked small holes in the eyes and wired up a couple of flashing LEDs. I mounted it on an old mop handle and stuck it in the ground. I added a braided deerskin headband with feathers, and now it looked like it was part of an ancient Indian burial ground.
The other skulls on the ground were more expensive....made from a thicker plastic, but I gave them a new paint job too. Here they are at night!