Every so often a big tweak comes around that gets me more excited than most, and Multify—a new tweak from John Corbett and Joel Einbinder—meets that criteria to a tee. Multify is an upcoming tweak that brings true multitasking to iOS in an easy to use and surprisingly stable package. Yes, other tweaks have attempted to do similar things in the past, but this is by far the best implementation that I've seen or used thus far.
Multify: an awesome new multitasking tweak for iOS 8