Artificial intelligences aren't going to take over Earth by building a bunch of robotic fashion models to karate-chop us to death. Instead, the A.I. takeover will come from a nasty nano-tech sludge that consumes all matter in its path to recreate itself endlessly. This "gray goo" scenario has popped up in novels by Walter Jon Williams, Rudy Rucker and Greg Bear, but it hasn't yet appeared in any major movies. Here's how we would tell a Hollywood-friendly "gray goo" story.
It's in your toothpaste!! "Highly evolved nanostructures" such as Bucky balls are already being used in toothpaste and face cream, among other household products. What if your exfoliating, revitalizing beauty cream suddenly turned eeeevil? The possibilities are as infinite as the spaces between molecules. Maybe the nano-structures aren't just passive, but actually contain tiny nanites that start eating your face? You could have a rash (so to speak) of corpses with melty faces, and our heroes have to figure out why, before...
...the awful countdown. There has to be some horrendous clock ticking down to N-day, the day the rogue nanites bust out and consume everything. Maybe the melty-face people are just the first wave, or maybe some evil nanomachines got activated prematurely by mistake. (Or maybe it's just an excuse to have some smooshy faces, which who doesn't love?) But there's a monster computer that plans to release all of the nanites at the same time, which isn't just immediately for some reason. (Or the nanites just get released by accident — but an evil AI is more fun.) Our heroes have to rush to stop it, but... they're too late.
The gray goo is consuming everything. It expands exponentially, so the more it consumes, the faster it spreads. In Wil McCarthy's Bloom, it only takes a few hours for gray goo to swallow up Earth's ecosystem. Similarly, in Rudy Rucker's Postsingular, the "nants" manage to swallow up the entire Earth within about a day. So the gray goo starting to be released should probably be the "break" between the second and third acts of the movie or TV show. (At the same time, our heroes should have an important personal realization, and confront something or other about themselves, blah blah blah.)
The nano-ooze should have a catchphrase. Nobody is ever going to care about nano-gunk that doesn't have a swagger in its voice. Maybe the nan-ooze speaks through your computer speakers, or grows a giant mouth, which says something like, "You Are Our Raw Material." Or something catchier, like "Your Biosphere Will Be Disassembled." (We'll save the truly dumb catchphrase, like "The Goo Will Be You," for the movie poster.)
So there's a program that can deactivate the gray goo, or maybe a firewall that it can't pass for some reason. But in order to deploy this magic-bullet code, our main character has to face his/her greatest fear. Or confront a mistake he/she made long ago. Or maybe our heroes discover that another batch of nanomachines can neutralize the first batch by altering their function.
We see the face of god in the heart of the goo. Once our heroes come face to face with the wall of goo, there really ought to be some sort of 2001/Sunshine-y moment of confronting the vastness of the micro-world and maybe coming up against the divine in everything. Maybe the nano-machines teach us an important lesson about what it means to be human, or the soul, or something. Like the Cylons in Battlestar Galactica, who always turn into spiritual guides when you least expect it. Everything gets all rhapsodic and we break out the wobbly lens so the gray goo can teach us some important lesson before it vanishes into a haze of mystification. That's your awesome gray goo movie right there. And they said it would never work.