Many years ago I had an idea to write a story about a guy who loses his wife and children to a monster attack. This is how he learns that such things are real and he becomes a Hunter to exact his vengeance. To start he gets a big knife and a big gun, a 10mm Glock 20. Along the way he meets an older guy who has been a Hunter for decades and teaches this guy some of what he knows. At this point he switches from a 10mm auto to a .410 revolver and starts making custom shells using salt, silver, garlic, teakwood soaked in holy water, ect. depending on what type of creature/entity he is facing. He sometimes puts a bit of everything into a shell he calls "The Sampler".
Then I was going to throw in a part where he's up against what he thinks is a vampire or werewolf but it turns out to be a human. This way I could have cool dialogue like:
"I've got 6 solid silver bullets with your name on them."
"Why? I'm not a werewolf."
"That doesn't really matter to the bullets now does it?"