TL;DR: Santa delivers physical objects to 95% of people (including adults) who ask for it in the form of a letter. He will start this Christmas and will continue until decided otherwise. And yes, he will deliver atomic bombs and AK-47's. How do we react?
Most of the parents tell their kids the biggest lie ever: Santa Claus does not exist.
Santa Claus does exist. However, as stated in this brilliant answer, his requirements to put people on the "Good" list were bit too high. Also, to be put on the "Naughty" list, you had to be worse than all serial killers combined.
As a result, Santa did not deliver a single present in the past 100 years. He did not even go on his annual journey during the night of Christmas, since there was no need for it.
We started to believe Santa really does not exist. And at some point, we started to tell this to our kids.
However, this year, Santa decided to rework his metrics of the "Good" list. (And he is going to rework only the "Good" list metrics, his "Naughty" metrics stay untouched).
His reworked metrics put almost every single kid (95%) on the "Good" list. He also manages to secretly copy all the letters addressed to him, so he knows what the kids wish for.
On December 25th, 2015, in the morning, loads of families will discover "extra" presents under the tree. These presents are going to be addressed to the kid wishing for them and contain exactly what the kid wished for.
How does society react?
To sum it up:
- 95% of all letters addressed to Santa, or to his mythical equivalents (Father Christmas, Weihnachtsmann, ...) are fulfilled.
- Santa delivers only physical (touchable) gifts which can be made. No wishes for "world peace" or "get my parents back together" can be fulfilled.
- If there is a kid on the "Good" list who wishes for an "untouchable" gift, that kid gets a gender stereotypical toy instead - a doll for a girl or a toy car for a boy.
- Only wishes for yourself are fulfilled ("I want a doll for my sister" is not fulfilled, but "I want a doll" is).
- Wishing for multiple physical (touchable) items is allowed. Any number of invalid wishes get converted to a single stereotypical toy, delivered in addition to valid requests (if any).
- Santa Claus is a mythical creature, he goes completely undetected and untracked during the night of the gift delivery.
- Should there be a camera or any other device able to spot an "intruder" in somebody's home, that device will malfunction for the time of the gift delivery. Afterwards, it will continue to work normally as if nothing happened.
- Presents are good quality, "A Class" presents made in the North Pole. Santa's elves are able to create a perfect copy of any branded product. So if you wish for a PlayStation 4, you will get a PlayStation 4, but made by elves (still identical to and compatible with a PS4 by Sony).
- Money and gift cards are considered "untouchable" gifts too.
- Wishes for live animals are fulfilled by delivering a plush toy in the shape of that animal.
- All untouchable wishes convert to just one touchable gift (you get only one toy car for wishing world peace and everyone having something to eat).
Edit: I know that such rules are unfair and kids in the first world will get double amounts of PlayStation and Xboxes, while a kid in the third world will get a toy car or a plush toy. But "fairness" of the gift delivery system is out of scope for this question.
Edit 2: Examples of how wishes are fulfilled:
Girl wishes for Nintendo Wii U console -> Gets perfect working replica of that console
Boy wishes for world peace -> Gets toy car
Girl wishes for a live shark and for everyone having something to eat -> Gets plush shark and a doll
Boy wishes for iPhone and Apple store gift card -> Gets perfect working copy of iPhone and a toy car
Edit 3: Please note that the current state of Earth is assumed in this question. So these gifts are given to you in addition to whatever your relatives bought for you, because they stopped believing in Santa and assumed he doesn't exist.