Novels often include the most ridiculous depictions of combat. Fantasy novels are some of the worst, but the problem cuts across all genres. If we want to broaden our scope we should include all of the following movie genres: action/thriller, science fiction, fantasy, martial arts, and war (although some war films have gotten much better recently). We can also include virtually anything shown on television.
Many offenses (but certainly not all) fit into the following categories:
Stormtrooper effect/Principle of Evil Marksmanship: bad guys are terrible shots. (Even if described as being lethal killers.)
Law of the Conservation of the Ninja: ninja (bad guys) are weaker in large groups. (A single ninja is nearly unbeatable.)
One-at-a-time attack rule: Large groups of villains will only attack one at a time.
Two friends of mine have written excellent blog posts on the topic or realistic combat:
Christian Cameron writes the best historical fiction I have ever read. In this blog post he writes about the nature of warfare. (The blog thread is actually about the use of elephants in ancient warfare.)
Mike Shultz' fantasy novel, The Sword of Memory, is being published in Germany this fall. In this writing advice column (click writing advice and check out Lesson 16) he discusses rules for combat realism in fantasy.
Nothing makes me want to drop a novel faster than unrealistic action/combat sequences. So follow Mike's rules and read Christian Cameron's blog and we will all enjoy a better reading experience.
Now go out there and hurt your good guys.