I did this once to a new co-worker that just moved into the area. I made a fake envelope and letter with the City seal and postage cancellation, and stuck it in with the rest of his mail.

The letter I "sent" him said that his pet snakes were in violation of a city ordinance against exotic animals. He was informed that he had 24 hours to get rid of them. He was furious, and ready to fight.

One could do this stating they have:
A pet that needs to be removed .
There car has too many tickets and is about to be impounded.
A warrant for their arrest.
Are about to be Audited or owe back taxes.
That they've won something

Anything that they know they are in the right about, or feel strongly about, that will get their emotions going. Or that will make them very nervous.

Step 1: Get Supplies

First thing you need is a letter that has come through the mail lately with a permit stamp or metered mail postage. City and state org. and corporations don't use stamps. The second thing is to go online and find a Logo for the agency you are pretending to be. You could scan one off of a letter if you already have one. These 2 things really set up the envelope to look official and help support the joke. You will need a scanner (or camera if you don't have a scanner) and printer.

Step 2: Create the Envelope

Scan off the permit/postage cancellation and save it as a picture. Then open Word or some other program that will let you address and work with envelope sized paper. Then put your picture of the postage and Agency Logo in the corners and type in the Address of your mark. To give it some even more authenticity, try to use the postage bar code across the bottom. Print this out and see how authentic it looks.

Step 3: Create the Fake Letter

Again put the logo on the letter and try to make a professional looking header and/or footer. Remember back to English class on how to make a professional letter. Recipients name and address at the top , Date, and then Dear Sir

Fill it in with whatever will make your target mad. Depending on how far you plan on taking it, add a phone number too. Put in a fake name and a number where the will reach a phone system, that will make them push buttons and never get them to a real person to answer the the phone.

Here is a sample of a termination letter
taken from http://www.writinghelp-central.com/termination-letter.html

(print Employee Letter of Termination on corporate letterhead)

CONFIDENTIAL

December 5, 2006

Thomas Zatinski
795 Gilmour St.
Apt. 508
Chicago, IL, 60611

Dear Thomas:

It is with sincere regret that I must inform you that your employment at Addison Systems Inc. will be terminated as of Friday January 31, 2006.

As you know, the Downsizing Task Force delivered their report to the general manager in late October, 2006. Among the task force recommendations was the elimination of all temporary and contract positions. Since you occupy a temporary position, your position is automatically subject to the task force recommendations.

I would like to make it absolutely clear that in no way does your termination reflect that the company is in any way unhappy with your work performance over the past 18 months. In fact, you have been highly regarded as one of our most productive contract staffers. Unfortunately, you and the other non-permanent staff that are being let go are simply a reflection of the general economic downturn in the fiber-optics industry over the past year.

In an effort to try to reduce the impact of this termination, the company has worked out a severance arrangement that will give you one week's pay for each month you worked beyond 12 months. In your case this will amount to six (6) weeks of severance pay. In addition, your medical and dental coverage will remain in effect until the end of the severance period. You will soon receive a letter from the Human Resources Department with all of the details on the severance package.

Thomas, given your qualifications and proven abilities, I am confident that you will be able to find another position in the relatively near future. If you would like, I would be pleased to write a recommendation letter for you, to help with your job search.

Sincerely,

Fred Shandling
Unit Manager

cc: R. Jackson, Human Resources

Step 4: Delivering the Mail

The hardest part, is trying to get them to open the mail while you're there. If it's a spouse or roommate, then it shouldn't be too difficult, just sneak it in with the rest of the mail. If it's someone you work with, then it really needs to be business related if they're getting it at work. Just don't forget to tell them it's fake....