1) Drive around the city. Locate his posted signs. Replace them all with fake signs that lead to porn sites or phone sex.
(Around here, one digit off on the power company number and a woman's voice answers by saying, "Hi! Are you feeling horny?" Last time I dialed wrong I was actually waiting for the correct menu item to be listed before I realized what had happened...about three heart beats.)
2) Plant stories in the local papers about how any gamer who calls a "certain mysterious number" dies within 24 hours by whatever was the most horrible way one of his characters died.
3) Call him up. Pretend that you've taken a first print
woodie OD&D set hostage. You'll blow the box up if he does not run about the city, answering a succession of pay phones and following increasingly bizarre instructions.
4) Get a reverse directory. Find out where he lives. Hide in his house one night and call him up from
inside his own game collection closet. "Have you checked...the modules?" Remember to wear a mask...Warduke, if at all possible.
5) Spy on him for a while and then steal his identity. Dress like him, re-route his email and phone calls to your house, compile a list of his enemies to murder for him and mail a mocking letter to the city paper...boasting of his plan to "kill...and kill again." Arrange a meeting in the mall to sell him your original copy of
Ghost Tower of Inverness. Don't show up...instead, photograph him from a distance and mail the photos to his house, along with shreds of an old
Monster Manual.
6) Adopt a super-villain personna. Get together a costume. Call him up and claim to be "The Shiller," or "GURPStron." Alert the media to your crime spree, challenging your rival to somehow stop you. Leave clues for your nemesis to solve your next evil deed...which always involves something ironic happening to rules lawyers.
7) Pretend to be an FBI "profiler." Call him up because he perfectly fits the profile of a serial killer who has been haunting Canada for decades. Work things so that somehow all of his murders are related to the number 144...which we all know is the number of pages in a Cthulhu/Melnibonean mythos
Dieties and Demi-Gods. Claim that his game collection is "evidence" that must be siezed for analysis.

Write him a whole bunch of letters in which you take on the roles of the various gods of the Greyhawk pantheon. Slowly...slowly...we work our way down to Zagyg...and total madness. Madness, I say!
9) Call his phone and ask him, "Do you have
Dragon #2?" IF he says"Yes," then you say, "Isn't it hard to clean off your shoes?"
10) Arrange to meet him in a cafe or other public place. Flash a few copies of
B2 and maybe a Dragonlance novel. Suddenly, your meeting is interrupted by 10-20 screaming soccer moms (basically, all your gaming buddies' mothers and wives). They wave BAD&D signs and shove cameras in his face. Claim that you actually work for 60 Minutes and this is a television sting operation to locate and expose "game pushers."
Anyway...just trying to help....
Mark