You open the door and see before you children dressed in Halloween costumes, you then...

I give them nothing! But take from them, EVERYTHING! 
 

Yeah! 100% of duders are assholes!

Candy. I'm not lame.

Peanuts. They must know the disappointment I knew so well every Halloween.

I remember those people who would give out pamphlets about dental care. Those people are the worst.

Yeah, candy. Also, razor blades.

When I had a remote controlled burglar alarm I would wait for them to walk up to the door and knock.. then set it off and watch them run away...

I miss those days.

I would go with the "classics", poisoned candy or an apple containing a razor blade...

Crunch or Kit Kat. They deserve to know what true deliciousness is.

I yell "Garbage Day" and then shoot them.

Even as a savage foreign bastard who doesn't follow or practise Halloween, I would get a big bowl of candy. I would even make sure it's good stuff, Starbursts and the like, because more than likely that bowl will be hella full by the end of the night.

As it is, I'm spending my Halloween night taking a girl to the ballet, and am actually excited for it.

Cigarettes. I don't smoke cigarettes, but I'll buy some to get kids hooked early.

If I had candy to give, that.

Whip out my... hard candy

Ice cubes.

Sacrifice them to Satan.

@ValiantGoat: You seem to have your holidays confused.

Usually I do my fly up and then tell them this is Australia and we don't celebrate Halloween here until we are adults and using it as an excuse to get wasted and hook up with slutty zombie nurses.

I then give them a 45 minute lecture (with supporting images and puppet show) on what exactly getting wasted and hooking up with a slutty zombie nurse entails.

You'd think they'd get the concept by now.

I don't have any candy, so I wouldn't open the door. I also don't have any decorations though, so the likelihood of anyone knocking on my door is pretty low. Also I live on the third floor in an apartment building. So yeah.

Yeah! 100% of duders are assholes!

Each gets a generous ladle-full of steaming hot creamed corn.

I give them nothing! But take from them, EVERYTHING! 
 

...take off my pants.

EDIT:

Also,

Nobody knocks on my door.

@Rainbowkisses: I thought I may have been doing something not quite right, but hey it's gotten me this far.

Heroin.

I won't be opening the door because I most likely won't be home.

@JasonR86: Fantastic, that just came to mind too.

I am dressed as Jimmy Saville, WHAT NOW KIDDIES

Can o' spinach.

What about free games? Zombies!!!

I open the door and give them the Stunner. To teach them the important lesson of not trusting anyone. In particular , no one should trust the Texas Rattlesnake.

Where's the option to say Trick or Treat first thereby negating there authorship on the term and legally being able to steal there candy?

I'd probably be pretty freaked out since we don't do Halloween here. Instead kids do the trick or treating thing during Easter.

Man this poll had such potential, needs more options!

You open the door then slam it in their face

You open the door and run away in terror

You open the door and give them an Angus Bacon and Cheese

You open the door and swear incessantly

Halloween should still be a horrifying experience for kids and adults alike! What is this fun bullshit.

I'm going to give out pictures of myself, then when the kids say, "What's this?" I'll say, "Eye candy" and wink at them.

I would post a completely untrue and somewhat random and unfunny comment on a videogame forum. If I was feeling particuarly racy it would include a giantbomb meme. I would then proceed to print out multiple copies of said comment, fold them up and present them to the children who knocked on my door. Finally, I would touch their shoulders and fake my own death, before getting used to my new office.
 
Or I would give them sweets, but no kids live here.

a homemade snickers bar, if you know what I mean.

@Hamst3r said:

a homemade snickers bar, if you know what I mean.

...shit?

@pyromagnestir said:

Whip out my... hard candy

Turn off the porch light and shut the curtains.

...are you a cop? You have to tell me if you're a cop.

Tell them to stop indulging in these Earthly past-times. No good can come of such intrusions.

@Sackmanjones said:

I give them nothing! But take from them, EVERYTHING!

*slow clap*

Chocolate covered rat poison, it saves them from the horrible damnation that is adult hood. Happy Halloween everybody.

@Sackmanjones: I salute you. Especially the part where the parents go "This is madness!" and you scream "THIS. IS. SPARTA!!" and kick them off the porch.

Who's home on halloween?

I don't. I don't live in a neighborhood. So if someone did come to my house wanting candy, that would be weird.

Kick them in the balls and steal their sweets.

Candy. Because toothpaste and healthy snacks are for nerds.