"Similar in construction to the Big Frigger power fist, this pneumatic-type power fist is a large metal glove with a piston and ram built in above the wearer's fist. The piston shoots the ram forward with every punch, allowing the fist to deal more damage than most unarmed weapons. Unlike the Big Frigger brand, this pneumatic-based power fist doesn't use energy cells to operate."-Fallout Wiki
Design: This is the power fist design from Fallout 3 & New Vegas; the design allows for free use of the actual hand and is therefore more ergonomic, useful and just overall better than the hazardous amalgamation of metal used in fallout 4.
Features: I've made one blendshape for the fist to actually extend so there's no need for difficult animations. Additionally I've added bones to all of the fingers to allow for gestures if you would like to add it to an actual model.