Earlier this week, Waka Flocka Flame sent out a tweet that read: “N the studio working on [this] gucci flocka album,” complete with a twitpic of a studio board. Since then, the Internet was in a tizzy about the possibility of the two Brick Squaders joining forces for a full LP. It wouldn’t be the first time two high profile artists jumped in the studio for a full-length, as everyone from Nas and Damien Marley and Jay-Z and R. Kelly to O.C. and AG and Bow Wow and Omarion have done it. And, of course, West Coast staple Murs is the collabo king with several such discs under his belt.

Whether or not Gucci and Waka’s joint project comes to light remains to be seen, but there are a host of other rumored projects we’ve heard over the years that have yet to make it to the masses. The XXL staff ruffled through its collective memory (and Google) to compile a list of promoted, rumored or even just mentioned collabo albums that have never been heard—yet.

Let’s know which ones we forgot, but, more importantly, which one do you really want to hear now.