My current mini obsession for merging of two games is taking the RIFTS RPG setting and jamming it in the Cypher System. I love the setting elements of RIFTS. But the rules! Oh the convoluted painful rules! In comes the Cypher system to save the day. With the new core rules system you can give this setting some great light weight rules and really focus on the part that risks falling by the way side under its rule system, The story !
Rifts is a fantastical post apocalyptic setting will all the right elements for a great cypher system game. After all the Cypher system all began with Numenera, very much like Rifts in its own way. As to the aspect of Cyphers and Artifacts. They Plug in well into a Rifts setting. Cyhpers make sense as lost tech much like they do in Rifts. Artifacts plug-in well also.
But Rifts is not the only setting that I have seen that I would love to see get a mash-up treatment. I mentioned Mass Effect FATE a few Posts ago. Or Cthulhu FATE would be a good mash-up as well.