The Monster of the Week cannot be killed with conventional ammunition, whatever "conventional" happens to mean for the show in question. Frequently, the script requires the police/army/whatever to demonstrate this with Five Rounds Rapid. A common variation in science fiction has a Monster of the Week which is not merely immune to energy weapons (lasers, phasers, etc.), but can actually absorb energy from those weapons, making it stronger. This is often set up as a surprise, so SPOILERS AHEAD. Examples of Immune to Bullets include: