If Grafted Wargear is equipped to player 1's creature but player 2 gains control of the Wargear and moves the equipment to one of player 2's creatures, would player 1's original equipped creature become sacrificed?
The creature would not be sacrificed. Each player can only sacrifice permanents they control; if a player is instructed to sacrifice something they don't control, they can't do it and the sacrifice doesn't happen.
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Lightning Bolts don't kill creatures. State-based actions kill creatures.