This is an very easy way to gain even more gems from monsters. You need the stakes gun (the one that shoot wooden pike) and the painkiller. Kill an enemy with the stakes and make sure that he is near a wall or anything that will make him go fly and "plug" itself to it (wall, floor, pillar ect). Then equip the painkiller, and use the secondary fire as FAST as you can on the body: The body will NOT fly away in the air, since its locked to the wall by the pike and you will be able to get up to 4 or 5 gems (each is worth 15$) for each monster.
It work better if you shoot in the torso of the monster, the arms or legs wont work as good because the cadaver will still react to the painkiller (moving very fast in unusual ways), making it a little harder to hit him.
If you use the cheat that prevent the bodies from disappearing, its even easier.
I also noticed (in the second demo) that the big skeletons guys with shotguns can give me "gems" in the form of rings that are worth only 10$, they give you that when you damage them to a critical point, and then you blow them out to bits with a rocket.
Submitted by David Bedard (Qc)