I'd love to hear about your favorite concept or idea you've read about or seen in scifi media.

My personal favorite is the Conjoiner Drive out of the Revelation Space series. These ship drives are dual drives on either side of a lighthugger and have a living being inside the drives to act as a supercomputer, which holds a wormhole open inside the drives. The wormhole links far in the past to the big-bang and uses the energy from the big-bang for propulsion.

In most scifi I've come across wormholes are used for FTL travel, and I thought this was such a unique and creative use of a wormhole it has stuck with me for years after reading about it.

So what are your favorite devices or ideas that have come out of scifi media?