Ashton Kutcher
Followers: 6.5 million
Sample tweet: "Scars are just reminders of obstacles we've overcome. Wear them proudly!"
Where would Twitter be today without Ashton Kutcher? In April 2009, at a time when folks were still trying to figure out what the social-media site was for — or had no idea what the heck a tweet was in the first place — Kutcher announced a Twitter showdown. Challenging an unlikely foe, CNN's Breaking News feed, to a duel, Kutcher suggested they battle it out to see which would be the first user to gain 1 million followers on the site. After a media storm and playful tweet war, Kutcher edged out CNN for the win. Though the publicity stunt was effective, it was Kutcher's back-and-forth tweets with his wife, actress Demi Moore (@mrskutcher), that kept users following. To this day, 6.5 million continue to gobble up every word of the famous couple's Twitter conversations (they've been known to tweet at each other while in the same room) as well as Kutcher's musings on everything from politics to the latest tech trends. Though Kutcher is now just the sixth most popular user on Twitter, he's still handily beating CNN Breaking News, which comes in at No. 19.