On any level in the game if you have a flamethrower use it on enimes and keep burning them until they are dead on the floor.
While they falling on the floor keep burning them until you decide to stop, then take a look at them and there should be a body part left on there Skeleton......!
We have more cheats and tips for this game here, Die Hard Trilogy 2: Viva Las Vegas cheats
Comments for this hint