Facial Dialogue

Facial Dialogue occurs when a character is communicating not just his emotional reactions or intense feelings, but entire reams of dialog using nothing more than their facial expressions and without saying a single word. When two characters do this to each other, it results in entire paragraphs of byplay, all perfectly understandable to the audience despite the entire exchange being silent.

Used correctly, such scenes can be as good as, or even better, than those with actual spoken dialogue.

Eye Take, Aside Glance and Fascinating Eyebrow may be used as part of the Facial Dialogue, but by themselves are only limited versions. Often the forte of The Silent Bob, The Voiceless and The Quiet One. Often featured in a No Dialogue Episode. It is just as often used by characters who are perfectly capable of speaking, but just don't in this occasion.

Has nothing to do with porn actresses talking to the cameraman after...well, you figure it out. Well, it might. But probably not.

Examples of Facial Dialogue include:

Anime

Takeo from Mahou Tsukaitai had literal facial dialogue at times, with his thoughts being written out on his face.
Kino's Journey has an excellent example in one episode: Kino is in the land of the people who drank nanomachines that transmitted every thought and feeling, and each eventually had to live apart from everyone. After the man telling the story finishes, Kino's pep talk causes him to realise something; he silently thanks her, and her expression clearly says, 'you're welcome'. She explains all this to Hermes to ensure we got the point too.

Comic Books

Duma, the Angel of Silence, speaks entire volumes with nothing but expressions in The Sandman. His gestures and actions also say (and accomplish!) volumes more than his partner, Remiel, despite his almost complete inability to shut the hell up.
The "intra-couple communication stealth mode" (between Empowered and Thugboy). Subtitled for the reader's sake.
Watchmen is famed for doing this as well as having dialogue, adding a lot of depth to characters. The most famous example is when Rorschach's landlord begs him not to reveal to her children that she is a prostitute - his silent response is fascinatingly difficult to decipher.

Film

During the opening robbery in Serenity, River and Zoe have a short conversation using nothing but facial expressions that goes something like, "That guy." "That guy? Are you sure?" "Are you kidding me or just an idiot? Of course I'm sure! That guy!"
Jake, the Plucky Comic Relief Sheriff's Deputy in Support Your Local Sheriff does this a lot. It was one of the things Jack Elam, the actor playing Jake, was best known for.
Gene Kelly has a few memorable looks, including one moment during the dance scene of "You Were Meant For Me" in Singin' in the Rain.
Akira Kurosawa was excellent at getting this out of Toshiro Mifune.
John Cusack had a deep and profoundly spiritual conversation with a baby using nothing but expressions in Grosse Pointe Blank.
As It Is In Heaven, a Swedish film, where in one scene two main characters have such a non-verbal conversation.
Some Silent Movie stars mastered this out of necessity - Buster Keaton, Charlie Chaplin, etc.
In Animal House, a lot of Bluto Blutarsky's "dialog" is this.
Gone in Sixty Seconds features one character, called "The Sphinx" by the other characters, making a phone call and using nothing but Facial Dialogue to do so.
In The Brothers Bloom, Bang-Bang has only two spoken lines of dialogue, comprised of only three entire words, and yet manages to be a complete Deadpan Snarker the entire film.
Dopey, from Snow White and The Seven Dwarfs, does this throughout the entire film.
Emma Watson achieved a certain level of notoriety for her "eyebrow acting" in the Harry Potter films.

Literature

In Trickster's Queen, Aly and Dove manage to hold an entire conversation this way:

Word of the arrests reached Balitang House in the early evening. Dove, furious, came flying into the workroom as Aly met with her pack. Aly smiled at her young mistress as sweetly as she knew how. They understood each other. Dove did not need to ask if Aly had known about the arrests. Aly did not need to tell her that she had the matter in hand. The girl turned and walked out again.

Live-Action TV

Simon Tam did this a lot in Firefly. It's probably genetic.
Stargate SG-1: Christopher Judge as Teal'c was the master of unspoken dialogue.
- Parodied in a supposed "flashback" in the episode "200". While he and an invisible O'Neill are walking down a corridor (O'Neill's location is given away by the floating coffee mug he's drinking from), O'Neill makes a comment about being invisible which Teal'c responds to with his usual stare. Since he can't see O'Neill's response, Teal'c remarks after a moment, "I assume I am staring at you stoically."
This is supposedly what got Peter Tork cast in The Monkees. He didn't speak during his interview, just communicated with over-the-top facial expressions.
Merlin: Merlin's face at 0:52
- Also, this scene from the same episode. They have their entire conversation silently and almost leave it at that until Arthur decides to verbalize it anyway—probably because he felt Merlin wasn't embarrassed enough.
  - Merlin and Arthur do this a lot, even when they're speaking out loud. I swear, put any of their scenes on mute and you'll get the idea and it will still be almost jut as funny. Or sexy. Or both, depending on the scene.
The "telepathic conversations" on How I Met Your Mother. Although we hear what the characters are thinking, you can still get the gist of it just by the expressions alone.
- Occasionally subverted. In "Bachelor Party", Robin attempts to convey an important message to Lily with facial expressions, and Lily interprets it as a request for a tampon. In "Doppelgängers", everyone else is having a telepathic conversation about Ted's hairstyle, and Ted's voiceover says, "What are we talking about? Nachos?"
According to the writers of Yes Minister, during filming Paul Eddington would deviate from the script by replacing his lines with an expression- in later episodes they actually annotated the script with "Paul doesn't have to say this line if he doesn't want to" where they expected this to work.
Used in Everybody Hates Chris While narrating, he says that his parents would try not to fight around them, but they did have their fights through facial expressions.
In the Star Trek: The Next Generation episode "Allegiance", Picard is abducted by aliens for the purpose of study. When Picard turns the tables on his captors, they return him to the Enterprise, but before they leave the bridge, Picard and the crew, communicating with only subtle facial expressions, trap the aliens in a stasis field to show them what it feels like to be imprisoned. Picard makes a point of the fact that he and the crew communicated this way.
The scripts for Frontline frequently had lines in parentheses if they were intended to be implicit in facial expressions or body language.
Mulder and Scully of The X-Files are infamous for this. Already masters at the Held Gaze and Longing Look, most scenes have an imbedded layer of subtext within the facial expressions. It makes their relationship look very intimate and almost make an onlooker feel as though they've walked in on something they shouldn't have.
Grey's Anatomy has a good conversation between George and Izzy. After waking up with an alcoholic blackout of the night before, Izzy remembers George cheating on his wife with her, but George doesn't. Later on, George's memory comes back, and he and Izzy share an entire conversation without speaking.
The first episode of Bugs courtesy of voice-triggered bombs.
Buffy the Vampire Slayer. "Hush."

Western Animation

Wallace and Gromit: Gromit. Although it's a necessity in his case, since he's mute. 'Cos he's a dog.