(I turned on G+ linking, so we'll see how that works with this post)
Dr. Who is has a Cybermen story in the pipe, and I guess maybe Neil Gaiman is behind it or something. I honestly have no idea. It's not that I dislike Dr. Who, but I tend to be about a year behind whatever current is. Just one of those things.
That said, I saw an image for the cybermen, and it's very nice and polished, with a few Iron Man notes, and it got me thinking about fast cybermen (in the same spirit as fast zombies). For the unfamiliar, cybermen are a villain cut from the very Dr. Who cloth of "Very terrifying, unless you do something radical, like run away".
It's easy to joke about this (insert a Dalek/stairs reference here) but it gets a little interesting when you think about what drives it. Basically, this is something that allows for protagonists to not be combat monsters - having enemies who can't practically be fought but can be escaped opens up a lot of leeway for character backgrounds. For a less violent show like Dr. Who, that's very important. Similarly, when a zombie story is really about a mismatched collection of normal folks, it's kind of silly to make them all ex military. And in both cases, it promotes problem solving outside of combat.
Translated over to an RPG, this is pretty easy to model with high defense, low attack enemies. Build them in such a way that the best a fight can do is break even, and you disincentivize fighting. Note, that this is very different from making high defense/High offense enemies - in that case, fighting is not only a bad plan, but it's also pretty lethal. The trick with slow enemies is not that they'll kill you in a round, but rather that if you continue to engage them, it will sooner or later go against you.
Now, is this something that's actually desirable in a game? Sure, at least sometimes. Slow menaces are really just disguised pacing and tension engines. Because they are relentless but escapable, they can be brought to bear any time things slow down without the risk of ending play. They drive hard choices through their presence, because "not running away" is always a possible downside. If you think of the menace as a meter that slowly fills, it's easy to see the pacing laid bare.
That is, suppose the zombies have a 3 box meter. When they show up, check the first box. You can fight them, and if successful, the box doesn't fill any further, but if you fail (or if you are trying to do something else at the same time), the second box fills. Run the cycle again, and if box #3 is filled, then someone is grabbed and taken down, simple as that.
Now, the advantage of abstracting that is that it suddenly becomes a great way to handle any threat that can be escaped, but not vanquished. It would, for example, be a great model for being on the receiving end of a manhunt, but it can be more abstract than that too, especially if you substitute in something other than running away as the deferral mechanism. For example, if you eat, rather than run, then it's a model for starvation.
In a round about way, I think this may be coming back towards Skill Challenges and the way very old Fate handled long challenges. Which mostly suggests I may need to dust off some of that thinking.
1 - Hell, if you ant to do a Talislanta/Apocalypse World hack, it's easy to add "the menace arrives" as an extra option to all success-with-consequences outcomes.
2 - Yes, technically, that's an insta-kill, but note that that it can be *deferred* by fighting, so the badass can protect the technician's back while he plants the bomb or whatnot. It changes the role of the fighting dude, but not necessarily in a bad way.