Today marked the 15th anniversary of the tragic death of Tupac Shakur with many stars paying their respects to the late rapper via Twitter. MC Hammer tweeted a picture of himself with Shakur and Big Boi confirmed that Outkast was slated to work with Tupac before his untimely death in 1996. Both Rev Run and rapper Mann pondered what Shakur's Twitter feed would read like. We're betting it would be filled with insightful musings, just as his music was. Timbaland, Sean Kingston, and Adam Levine all tweeted simple RIPs in their tributes to the rapper while Cataracs and Ciara declared their love for one of the best MCs of all time.