It gets a little heady, but this Wired article does have a good analysis of weapons used in monster movies, and how they might actually be used in a real-life monster situation.
How To: Stop a 500-Foot Monster (Think Missiles, Not Bombs) | Danger Room from Wired.com
Back in the old days, things were fairly simple. When King Kong climbed the Empire State Building, he could be taken out by a squadron of Curtiss SB2C Helldivers . But since then there has been some inflation and apes 20 â.. 45 meters tall (Wikipedia’s estimate) are small stuff.
The giant ants in Them! still weren’t that gigantic, and the army could deal with them using poison gas and flamethrowers. But by 1955, when a mutated Tarantula the size of a skyscraper turned up, the only solution was to call the Air Force. Bombing with high explosive had no effect â.. presumably the creature’s exoskeleton was too tough. In the end napalm did the trick, setting the creature ablaze (is chitin really flammable?). It may have helped that the pilot carrying out the strike was one Clint Eastwood, then an unknown bit-part player.