I'm looking for a way to manually rotate a player's torso just once, and I've been looking around for awhile, so I'm wondering if it's possible?
Well, you need to CFrame the Toros, the rest of the body parts and stuff will go with it:
Torso.CFrame=Torso.CFrame*CFrame.Angles(math.deg(), math.deg(), math.deg())
Play around with the numbers. math.deg() will convert any number into a degree of rotation.