Detachable arm in Gamera vs. Viras
My favourite moment from Gamera vs. Viras is when the heroic child-stars of the film attempt to lasso an alien, which leads to an Nobuhiko Obayashi-esque airborne arm detachment.
Viras (バイラス Bairasu)
Viras stands alongside weirdos like Hedorah as one of the oddest looking kaijū in monster movie history. A deformed squib with the face of a bird, there's something strangely creepy about the big lug.