One that comes to mind is Cain's Offering, which was a one-off project that featured an all-star cast of Finnish power metal (Timo Koltipelto of Stratovarius, as well as the two primary songwriters of Sonata Arctica,) and IMO, was significantly better than anything their original bands have released in the past 7 years, and yet it went practically unnoticed. I wish they'd do another album.