If you don't wanna risk an exacto knife, just put a screwdriver in the hole at the base of the torso and use it to gently pry it open. That's usually how I do it unless I think it's glued (as in the case of the BJ's 8 pack Storm Shadow and any of the Ninja Force Figures), then I pry with the screw driver and slide an exacto knife to work the seam slowly.

Also you could leave it in the feezer for a bit. That tends to make the glue brittle and will make your work easier.

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