How do you out-shapeshift another shapeshifter? I kid you not:
Scissors cut paper!
Rock blunts scissors!
Hammer smashes rock!? Now you're just cheating, Proty. I guess if you don't want the fight to run on an infinite loop...
(From Adventure Comics #364, January 1968)
Comments
1) Dynamite blows up rock; scissors cut the fuse on dynamite. It's very logical.
2) For those who try to cheat by looking at the other person's hand motions, it's harder to cheat with dynamite (a single finger). So whatever you throw it's a fist, with 0-2 fingers. All three options look the same until thrown; there's no "tell" of the wrist turning to throw paper.