I'm still waiting for a really good Cybermen story on Doctor Who. (On TV, that is. "Spare Parts" got it right on audio, in ways that I'm about to explain.) Oh, sure, we've had lots of stories where the Cybermen show up, and even some where they do somewhat interesting things, but it says a lot that the coolest Cybermen story I can think of is mainly memorable for them getting their butts kicked by the Daleks.
The problem is that nobody really seems to understand what makes the Cybermen work, and I include their creators. The horror of the Cybermen isn't that they're tough, or that they have laser blasters, or that they have a cool catchphrase (which, apart from anything else, they don't. "DELETE!" sounds like the off-brand Dalek knock-offs.) The horror of the Cybermen is that what they do makes perfect sense. They want to convert every human being into a Cyberman because they genuinely know--not just believe, know--that it willl improve their existences, and they will never stop because they know they're right. The horror of the Cybermen isn't, "DELETE DELETE DELETE", it's "You will become like us."
But everyone writes them like big stompy villains who sneer and boast and preen and strut. For bad guys who aren't supposed to have emotions, they certainly seem to get upset a lot whenever anyone challenges their worldview. Instead, they should be calm, remorseless, and entirely certain in the rightness of their attitude. To the Cybermen, human beings are suffering from a mental illness that makes them irrationally attached...to irrationality, ironically enough. These poor people believe that their brain disorder somehow gives their life meaning, and need to be forced to undergo conversion for their own good. It's unfortunate that they can't understand how much better life is with a superior body and none of the distractions of emotion, but they will. Once they undergo the process, they'll understand just how much sense it makes. And then they'll help to convert others.
My idea for a Cybermen story involves a small group of Cybermen setting up shop on a space station, promising that they will not use violence or force, and simply asking people to volunteer for the process--convincing them, through the logic of their position. Yes, being a Cyberman means an end to joy, but it also means an end to fear, an end to rage, an end to misery and suffering and pain and sorrow and all the weaknesses of the flesh. There are some people who would gladly give up their flesh and blood if it just meant the pain would stop.
Their endgame plan, of course, would be to convert the unwilling by force once they had enough recruits. Because deception, while again unfortunate, is sometimes necessary when dealing with the irrational. It's like dealing with a madman, sometimes. But the Cybermen have a cure for that.