They've collaborated on hit songs together. They run in the same circle. So we should have known that it was only a matter of time before Kanye west and Rihanna teamed up for a tour. Yesterday, Live Nation leaked a bill for a "Kanye & Rihanna" tour, rumored to kick off this summer in Estonia, though spokespersons for the musicians have yet to comment. The news got us thinking what other singers we would love to see collab with each other. Erykah Badu and Lauryn Hill, if you're reading this, we think you'd go great together!