I thought of this myself. I apologize in advance if it's been posted before.
First step is to prepare a macro or a copy paste something like this
/dnd WE'RE NO STRANGERS TO LOVE YOU KNOW THE RULES AND SO DO I A FULL COMMITMENT'S WHAT IM THINKING OF YOU WOULDN'T GET THIS FROM ANY OTHER GUY AND I JUST WANNA TELL YOU HOW I'M FEELING GOTTA MAKE YOU UNDERSTAND NEVER GONNA GIVE YOU UP NEVER GONNA LET YOU DOWN NEVER GONNA RUN AROUND AND HURT YOU... (etc)
Now, go to a city and say something like this:
/2 Giving away my T6 rogue, I'm quitting wow First person to whisper me gets him
As soon as you post that, immediately put the /dnd macro on.
Now sit back and laugh as the noobs get rickrolled.