[Swampghost]

Over the years I've think that I've heard it all.
From an old swamper hunting ground blinds, place about a 1/2" dry stick on a rock and snap it with your foot. It works most of the time.
From another who carried antlers and used low stands, drop the antlers together. It works too.
Grunt calls as long as they leave both hands free or you can pull them off convincingly by mouth.
My favorite is still the bleat by mouth, 'mmaaaaaa'. The dummies just can't seem to resist it.