Here’s a catalog of ‘Twitter Experiments’, official Twitter accounts that offer special services.
@MagicRecs- ‘This is a Twitter experiment. Follow me to receive instant, personalized recommendations for users and content via direct message.’
@EventParrot- This is a Twitter experiment. Follow me to receive direct messages that help you keep up with what’s happening in the world.
@AchievementBird- This is a Twitter experiment. Follow me to receive analytics via direct message. DM me back with feedback!
If you come across any others, comment or let me know.