I kicked a caffeine addiction by getting a cold/flu type thing. I figured I was already in pain, so the withdrawal headache wouldn't really show, and I was staying home and not seeing anyone, so the chance of me committing enraged homicide were slim.
These days, I have the occasional cup, but I'm not a regular coffee-drinker, and an awful lot of coffee, which I would previously have drunk quite happily, now tastes horrible.