In "Drone"[VOY5], a super-drone is created when a transporter mishap mixes the Doctor's 29th Century future-tech portable holo-emitter and some of Seven of Nine's Borg nanoprobes. The be-nanoprobed holo-emitter is thought to merely be damaged and is left alone in a lab for later repair.
Instead, the emitter is assimilated, and the new Borgified hardware assimilates other nearby equipment and, later, takes a sample of DNA for a biological template. After a day of super-speed maturation, the super-drone emerges.
What's amazing here is that the entire plot of the episode is based around the idea that stray nanoprobes from Seven of Nine which merged with the portable holo-emitter assimilated it, extrapolated its technologies and developed new capabilities therefrom, developed a plan to extract a tissue sample so that the DNA (and presumably the cellular material) could be used as a biological template from which to begin crafting a full-size lifeform, designed and built a unique Borg maturation chamber out of assorted nearby Federation components, and so on.
Let's look at a few choice bits, with thanks as always to Chakoteya.net:
SEVEN: This technology resembles a Borg maturation chamber, but many of the components are unfamiliar.
SEVEN: He was punctured by an extraction tubule. It removed a tissue sample. There are residual nanoprobes surrounding the wound. Their encoding sequences are identical to my own.
TUVOK: Your nanoprobes? How?
SEVEN: I don't know.
TUVOK: Take him to Sickbay. What are you doing?
SEVEN: I will be recognised as Borg. A drone, but unlike any I've ever seen.
TUVOK: It appears to be in the foetal stage.
SEVEN: I don't understand. The Borg assimilate. They do not reproduce in this fashion.
JANEWAY: Where did he come from?
SEVEN: I believe it was created here in the science lab. When the away team beamed back to Voyager there was a transporter malfunction. Our patterns merged briefly. It is possible that some of my nanoprobes infected the Doctor's mobile emitter.
TUVOK: They began to assimilate.
SEVEN: Yes. Nanoprobes are encoded to utilize any technology they encounter. Once it assimilated the emitter, it began to transform this diagnostic station. When Ensign Mulchaey entered the room, they sampled his DNA.
JANEWAY: Using his genetic code as a template to create a lifeform.
EMH: Well, he appears to be human for the most part. Borg implants comprise approximately
EMH [OC]: Twenty seven percent of his body.
TUVOK: Curious. His body plating is composed of polydutonic alloy
EMH [on monitor]: Just like my mobile emitter.
SEVEN: The nanoprobes must have extrapolated that technology. It could explain his unique design.
TORRES: Wait a minute. The Doctor's emitter came from the twenty ninth century. It's five hundred years more advanced that anything we've got.
TUVOK: It is logical to assume this drone will be equally advanced.
TORRES: A twenty ninth century Borg.
TUVOK: In essence.
EMH [on monitor]: I've located my mobile emitter. It's embedded in his cerebral cortex.
SEVEN: The emitter has been adapted to serve as part of his central nervous system. It controls all autonomic functions.
EMH: That means we can't remove it. Not without killing the drone.
TUVOK: Has it contacted the Borg collective?
SEVEN: No. I have dampened it's proximity transceiver.
TORRES: For now. What about when it grows up?
[Ready room]Y'know, I really don't know why the drone would await instructions from the Collective. The nanoprobes themselves seem to be quite capable of independent thought and creativity, if not individually than at least in aggregate. As of "Inside Man"[VOY7], Seven is said to have 3.6 million nanoprobes within her. Assuming they are evenly distributed, then only some thousands could've infected the mobile emitter just based on a quickie volumetric guesstimate.
JANEWAY: Reactive body armour? Multidimensional adaptability? Internal transporter nodes?
SEVEN: The drone possesses superior technology. It will fully mature in less than two hours. However, its Borg shielding is not yet active. We can still terminate it, but we must act quickly.
JANEWAY: Hold on a minute, Seven. I want some answers first. What normally happens when a drone disengages from the maturation chamber?
SEVEN: It awaits instructions from the Collective.
And yet, these thousands, perhaps with computing support from the mobile emitter itself, were sufficient to do a great many things. Extrapolating technology and designing new things from it is not exactly child's play.
All this having been said and pondered for awhile, it wasn't until I was writing the paragraph above that I realized that the mobile emitter's computing power could have been tapped for these tasks, and after the relevant technologies aboard it were extrapolated and duplicated, the emitter itself was 'discarded' as a mere nervous system controller.
Still, however, Seven's statements are clear that the nanoprobes themselves are designed to do precisely what they did, which in this case was to assimilate . . . to take control of . . . and make good use of a 29th Century device which, it goes without saying, they had never encountered before. Even if they adapted its processing power for their own tasks to aid in later design efforts, they remain amazing for being able to do that.
Certainly we've seen near-magical transformations of NX Class engineering components with nothing more than the injection of Borg nanoprobes, as seen in "Regeneration" when a drone simply injects a plain-ish area and Borgifies it, so this seems to follow.
Put simply, the nanoprobes are extraordinary tools, and given their capabilities it is interesting to ponder something like the Borg having their own SG-1 Replicator moment . . . after all, if they're so capable, why do they need the fleshy bits at all? Why do they need the Queen? Certainly the Queen's resurrection could be nicely explained if she were merely a manifestation of the nanoprobes. But, then, why just one? Why not have queens everywhere?
And while we're pondering, it's easy to ponder that the Borg may have been conquered by their own technology . . . turning the Borg into victims of a Terminator or Galactica-esque failure to contain their own creation.
We can even imagine it starting again. Can you imagine a Borg Civil War fought between drones and their nanoprobes? SG-1 Replicators, eat your heart out.