Hahahaha! Just seeing that again threw me into fits of giggling.
…
One is when Homer pushes one transporter device into the bathroom and leaves the other in the living room, then proceeds to pee in it.
One isn’t so much a sight gag, but:
Homer: Boy, as long as you live under my house, you’ll live by my rules! Now wrap that sausage link in bacon!
Bart: But Dad…
Home: No arguments, boy! Butter that bacon!
Bart: Dad, my heart hurts!
What was the “conquer” sight gag? 
Carl uses “I concur” and his idiot buddies are mystified. He explains that he got a “word of the day calendar.” Flash to the calendar showing “conquer.”
After much fruitless Googling I wonder if I imagined this - at some point did Homer consult to crib notes on his hand saying something like: “Kenny = white; Carl = black”?
If that is in fact actually real that is my favorite.
The episode where Apu puts in gas pumps. When Skinners bumps the mortar guy and a minute later the A from the gas station sign drops silently into the ground behind him. Slayed me.
Any of the chalkboard gags or couch gags. My favorite chalkboard gag: “I will not waste chalk.” Followed closely by “South Park, we’d stand behind you if we weren’t so scared,” after the Mohammed censorship flap of episode #201.
“Homer, you have it set to whore.”
From the same episode, I love the sign that says “Cultural museum: cart your arse on in.”
Another one of my favorites is the first time they showed Homer using his reading glasses.
Can only find a German version, but from one of the first seasons when the trauma vet pitches the hamster into a little bucket and basket hoop.
This is both an image and sound gag: When Marge got her black eye she used a can of Irish Strength Shiner-B-Gone with Too Ra Loo Ra Loo Ra in the background. Fucking ballsy.
From the episode of The Actors Studio where the entire cast of the The Simpsons was on a few years ago:
“Moe’s Tavern - Home Of The World’s Smallest Large Screen TV”
When the Simpsons get a trampoline and all of the injured kids are laid out as far as you can see in an homage to “Gone With the Wind”.
Another sign outside a building – “Morningwood Penitentiary”
In the episode “Mad Mad Mad Mad Marge”, when Marge, escaping from an insane asylum, tries to blend in with a marching band, and the band turns out to be from the asylum, and she marches right back in with it.
Even better: the band are wearing orange jackets that match the one Marge is wearing, and they’re wearing large blue hats that look like her hair.
Yes. It’s from A Tale of Two Springfields where the town gets split into two different area codes (“I hate this new area code. Like I don’t have enough to remember already.”)
Your location is what keeps it fresh in my noggin meat.
Not sure if it counts a sight gag but I love it.
When they go to Australia and Homer and family are standing just outside the US Embassy and Homer is jumping back and forth between countries with one foot in each saying,
“Now I’m in America.
Now I’m in Australia.
Now I’m in America.
Now I’m in Australia.
Now I’m in…”
And the Marine guard punches him in the face and says," Here in America we don’t tolerate that kind of crap, Sir!
Bart is the young Mozart. There are signs over the two doors of the Vienna Opera House. One says “Fops,” and the other says “Dandies.” LOL!
