Bob Marley was/probably still is, the greatest stoner of all time. Jimi Hendrix was quite the pothead but not to the same extent.
And contrary to popular beleif, Marilyn Manson (Brian Warner) had only smoked pot only once and described it as horrible. Then again hes a 'very frequent' cocaine user. He's still a good artist (I think) because if you read his autobiography it gives you a new perspective on him. I don't really know why I'm saying this. But I ramble sometimes. Just had a good smoke.