Deer-Scarer

Entirely inspired by http://www.thingiverse.com/thing:224441, but in less parts (3 STLs, print the peg twice).
Prints as base and arm and peg, sits nicely once pegs are glued.
Thing sits under tap/gentle stream/severed limb, fills slowly with liquid, until nearly full, then it tips forward, empties tapwater/fresh-foresty-water/blood, then the not-hollow-bit that sits below the peg once again is heavier, the arm resets.
Prints well with Ultimaker 2, sliced with Cura to be "hollow", aka criss-crossed lines, otherwise the lower arm may be too heavy for the hollow upper arm to outweigh once filled.