Also known as a magnetic fusion drive, or a mega-ion drive.
A staple of high end sci-fi is the replicator or the nano-assembler. There is a much more practical and less technomagical way to achieve the same goal. The exciting thing is that this technology exists now, and we're getting much better at it.
Another real world thing. White tea. Can only be picked two days a year, the two days before the flowers blossom. Could be a similiar plant that...is the deadliest poison known, cure known diseases or psychosis, or a potent herb that just tastes awesome.