Well, I'm glad to find out that someone finally took up this fourth "Six of the Best" Challenge.
Rather predictably for science-fiction spanking stories, three of these selections of mine involve mechanical and/or artificial spankers (in a direct physical sense), one of them involves artificial spankees (which strikes me as quite unusual), one involves virtual reality and one involves time travel.
"Andromeda" Parts One & Two by Medici [X/M, fairly short]A lone astronaut on a four-year space voyage receives a gift from his ex-wife, whom he used to spank, it being a female android which is designed to extract retribution atop his naked buttocks for the entire trip. 'Mistress Strict' turns out to live up to her self-adopted name and even appears to expand her original programming.
"Asteroid to Meteor to Meteorite" by John Graves [F/M, fairly short]An extremely low-probability event occurs, resulting in a scientist receiving corporal correction from his demanding wife--however, her method of administering it is highly unusual, perhaps even surreal.
"Family Values" by Koala Bear [F/XXX, short]A mother is greatly gratified by soundly spanking her three young children for fabricated reasons, reveling in their distressed reactions--yet the situation is actually a problem only for overhearing sympathetic neighbors, not her red-bottomed and bawling spankees.
"Martha Learns a Lesson" by Dr. Keate [X/FFFF, fairly long]Living under the authoritarian regime of the anti-feminist Brotherhood, a 'naughty girl' earns herself a thorough bare-bottom thrashing in a spanking booth, even though her offense against 'Good Order' appears to be a trivial one.
"Zero G" Part One by Flatfish & Part Two by Gloup [X/FF, fairly long]On a space station, a talented young woman programs a multi-tentacled robot to both pleasure her erotically and spank her very soundly in a zero-gravity exercise environment, only to have a feminine rival inadvertently end up receiving that same treatment.
"The Tipping Point" by John Benson [F/M implied, fairly short]In science-fiction accounts, tampering with past events often has negative results, yet in this case the time-traveling mission to alter a sexual predator's psychology is projected to be successful--if it's carried out properly by the chosen female operative.
I found all of these to be quite enjoyable reads...

--C.K.