The Couch

What's a Dom Com without a couch? It's usually center-stage and positioned so that anyone sitting there is facing directly into the audience; presumably it's right in front of the Fourth Wall. Sometimes a TV is set between it and the audience. The couch is typically set in the center of the room, rather than pushed against a wall, so that standing characters can converse with sitting characters while both are still facing the audience.

And everybody sits on The Couch at some point during each show. Even the dog. They probably sit in the same place every time, too.

If you can remember the shows, you can almost certainly picture the living rooms (or coffee bar) and the requisite couch.

The couch is, of course, prepackaged in Standardized Sitcom Housing (however, you do have to buy your own TV), and can often be found in a Social Semi-Circle. (That said, don't put two gamers on it). And you can't have a Couch Gag without it.

Live-Action TV

According to Jim: There is a couch in the living room the other cast members use, but Jim normally sits in his chair to the left of it.
All in The Family (no, not the two chairs in the center. Over to the right some, by the door, under the window—yeah, there).
Are You Being Served had its own version of The Couch: the long cafeteria table at which every character sat on the same side, so the set could be built with only one wall.
The Big Bang Theory: Possibly referenced in an episode where Sheldon's "spot" on the couch is dirtied by a paintball and being the high-strung, type-A nerd that he is, he has to deal with either finding a new place to sit or simply turning the cushion over, which he refuses to do, because it doesn't have his butt imprint on it. Before the couch was there, it was simply a lawn chair Sheldon used as his "spot."
The Cosby Show
Coupling has the couch and chairs at their oft-frequented bar. Occasionally, they'll sit in another spot, but if you need to gather all six of the cast around, it'll be on the couch.
The Dick Van Dyke Show: Don't trip on the ottoman!
Everybody Loves Raymond
Family Ties
Frasier played it straight with an actual couch, but Martin Crane's nearby banged-up old recliner was arguably more well-know, well-liked and certainly more frequently used in the series, to the point of becoming the center of a border-line Running Gag.
Fresh Prince of Bel Air
Friends had several—in the various apartments and in Central Perk. Some sets don't use the facing the audience portion of the trope.
In The George Lopez Show, George's kitchen table is like this.
The Golden Girls had two of these: The actual couch, and the kitchen table. It's about a fifty-fifty toss-up which one was featured more prominently.
Growing Pains
Happy Days
How I Met Your Mother
- Not only is there a couch in the main apartment, the cast never has a problem getting the exact same booth in a crowded, lively bar. One episode shows that this was because one of the bartenders would shoo away anyone sitting in their regular booth. The writers wanted to avert the latter and have them more realistically sit in different places at different times, but they were told this would be too expensive.
- Barney's couch faces the Fourth Wall, which in his apartment is a TV.
iCarly
The Jeffersons
Married... with Children
On M*A*S*H, the cots in the Swamp frequently served much the same purpose.
Men Behaving Badly: The sofa became practically another character in the show, and the last non-special episode, "Sofa," was even about its replacement.
One Day At a Time
Red Dwarf, being set in space, had no actual couch. This was actually cited as a reason why it wouldn't be funny in one of the rejections the writers received when they were trying to pitch the show. Their answer to that was to use the man's name as an insult in a second-season episode. It's "You're a total Gwenlan, Kryten." Various locations served as a sort of couch substitute - initially, Lister and Rimmer's bunkroom fills the role, later Starbug's mid-section - but usually, the characters meet up where the plot requires them to be.
Roseanne—And, damn, that couch (and the ever-present blanket flopped over the top of it) was uglyyyy!
The Royle Family: Although neither the sofa or Jim's chair are the standard "facing the fourth wall" set piece. Instead, the camera freely shifts around the room and we do even get to see the fourth wall a lot.
Rules of Engagement has one in each of the two couple's apartment. There is a room in the back of one apartment that has two chairs facing a TV against a wall, periodically used.
Scrubs: The one in JD and Turk's (later Turk and Carla's) apartment.
Seinfeld
Still Standing had the couch. In fact, most scenes took place in the living room in the vicinity on and around said couch.
That '70s Show: Eric's basement/house.
Three's Company
3rd Rock from the Sun - the Solomons' loft apartment as well as any other character's home (Mary, Don, Nina, etc.).
- Subverted in that the Solomon's don't own an actual couch. They make do with two or three ratty chairs and an ottoman. In the episode when Harry gets amnesia, the first thing he says when he sees the living room is, "No sofa, that's weird."
'Til Death: Played straight with a couch, though the easy chair to the left of it was used just as often. The other is a literal one in front of the kitchen, of the TV variety. Rarely are people seen in the kitchen when this second couch was used.
Two and A Half Men has 2. The first is the kitchen table, where normally only 3 of the 4 seats are ever used.
- Subverted in one episode. The kitchen table hosted Alan, Lauren and their children around the table. While the least important character has his back to the fourth wall, a camera cuts around to show him face on, and the fourth wall is indeed visible behind him.
In one episode of Yes, Dear, Greg moves the couch so that it faces away from the Fourth Wall, arguing that the previous arrangement made no sense. His wife complains that it doesn't feel right somehow.

Theatre

All of Mary, Mary takes place on one domestic set, which includes a sofa.

Web Original

The RPG Fanatic: Almost every episode involves the RPG Fanatic sitting on his couch playing videogames.
Atop the Fourth Wall: Linkara's futon.
Present in Manwhores

Western Animation

The Simpsons (which even became famous for the Couch Gag)
Family Guy, though the couch and furniture often move around for the sake of keeping a wide number of characters on the screen at once.
Beavis and Butthead: The title characters were well known for sitting on a couch and critiquing music videos.
Similar to Are You Being Served? above, Sidekick during lunch has the four main characters all sitting on the same side of the table.