With all the mentions from the Casino episode ($pringfield, which just might be the bst episode ever, at least funniest) I’m suprised no one hjas mentioned:
Lisa: (sees her horrible Florida costume) I’m not a state…I’m a monster!
Homer: No, you’re not a monster. The only monster here is the gambling monster that has enslaved your mother! I call him Gamblor! And I will free you mother from his neon clutches!
Ah, good to know.
The Earth is about to be destroyed but there’s a rocket ship to save the most valuable people. Marge and Lisa are allowed on board, but not Homer and Bart. Desperate to not be left behind, they notice another rocket about to take off and scramble aboard. They are greeted by Tom Arnold and notice with suspicion that the passengers also include Al Sharpton, Dan Quayle, Courtney Love, and “Aaaaa! Rosie O’Donnel!”, and the ship is sent flying into the Sun.
You forgot the best part-they couldn’t even stand being on the rocket for the few minutes it would take them to get to the sun and burn up, so they eject into space, giving huge sighs of relief as their heads swell and burst.
The parody of “Bram Stoker’s Dracula” was hilarious.
Homer: We’ve been invited for a midnight dinner at Mr. Burns’ mansion in…PENNSYLVANIA!
Lisa: We have to kill the head vampire—Mr. Burns!
Homer: Kill my boss? Do I dare live out the American dream?
Homer: Where would a sick, twisted, isolated anti-social freak hang out?
Lisa: I’ll check Radio Shack!
Homer: We’ll be staying at the Springfield Palace Hotel where we’ll get free food, free room service…oooh, “Free Willy”!
Skinner: Justice isn’t a frivolous thing Simpson. It has little if nothing to do with a disobidient whale.
Vendor: We have Mountain Dew or Crab Juice.
Homer: Uggggghhhh, yeccckkk, gross. I’ll take the Crab Juice.
Marge: I’ve always wanted to be part of a Broadway audience! (a line I’ve used more than once)
Well, I’ll be darned . . . it was Mandy Patankin.
I have so got to find a way to use that next time I’m at the casino.
Homer, comforting Bart: There, there…shut up, boy.
From the Beer Baron episode (18th amendment?)
When the stills begin to explode in the basement, and Homer runs down to check them. BIG explosion. The shot from the bedroom through the window to the lawn, with Homer rolling around to put the flames out, has actually caused me to pass out.
(I was very drunk at the time)
Geez…how could we forget El Viaje Misterioso de Nuestro Jomer (The Mysterious Voyage of Our Homer).
Homer: In your face, Space Coyote!
Homer: Note to self: Don’t do anything.
[Lisa and Bart are brushing their teeth, and look out the window to see Homer’s silhouette from the lighthouse light]
Bart: Is that Dad?
Lisa: Either that, or Batman’s really let himself go.
Coyote: There is a lesson you must learn.
Homer: If it’s about laying off the insanity pappers, I’m WAY ahead of you.
Homer: We don’t have anything in common. [opens the record cabinet, with “Marge” and “Homer” sections] Look at these records: Jim Nabors, Glen Campbell, the Doodletown Pipers. Now look at her records! They stink!
Homer: [Looking for his soulmate in a newspaper] Hello? Is this… [reads his paper] GBM? Uh, yeah. I read in the personals that you were seeking a soulmate. Well, I also like rainy days and movies. Uh-huh… [apprehensively] Uh, no, I don’t like that… Or that… No, it’s not that I’m afraid. [very quickly] I’m
going to hang up now, bye-bye.
Homer: Wow, Marge, you really do understand me. See, I thought we weren’t soulmates because…
Marge: …we had a fight?
Homer: Right, and we don’t like the same things. It’s like you’re from Venus…
Marge: …and you’re from Mars.
Homer: [resentfully] Oh, sure, give me the one with all the monsters.
From I Am Furious (Yellow):
Homer: I’m just passionate, like all us Greeks.
Marge: No, you’re angry. Look, you’re punching the cat right now.
Homer: [Looks at right hand, which is holding Snowball. His left hand is punching the cat in the belly] Oh my god, you’re right!
Podkayne, if it makes you feel better, I’d have bet a lot of money it was Hugh Grant. Oh well.
I think it’s impossible to pick one, greatest simpson’s moment, but we’re getting a lot of the best. One of my favorite is:
Homer singing:
“Stealing, stealing, stealing a car for moe.”
In fact that whole episode, where Moe meets a woman (I think the voice of helen hunt), is one of my top 5 favorites.
Yup, it was Helen Hunt, who, at the time, was married to Hank Azaria, who voices Moe.
Or the the classic Homerism:
Gimmee some inner peace or I’ll mop the floor with yah!
(Great for parties)
The one line I’ve used myself several times is when Homer was jumping around dancing after he did something clever;
“I am so smart, S-M-R-T. I am so smart S-M-R-T.”
Two more great lines (it woulda been three, but somebody beat me to Gamblor!)
From Boy Scoutz 'n the Hood:
Captain McAllister: Arr, here be a fine vessel – the yarest river-going boat there be.
Homer: (excitedly) I’ll take it!
The raft sinks
Cap’n: (disconsolate) Arr, I don’t know what I’m doing.
From Homer Goes to College:
Homer: You’ve won this round, Dean… but the war isn’t over. (leaves)
(The Dean’s phone rings, and Homer is seen in the background using a phone)
Dean: Hello?
Homer: (disguised voice) Hello, Dean? You’re a stupid-head.
Dean: Homer, is that you?
Homer: Aaaaaugh! (runs away)
You got the schools reversed. Later in that episode, Homer disparages Lenny and Carl’s alma mater (Springfield A&M), calling it a “cow college”.
Lenny: You only call us a cow college because we were founded by a cow! [defiant nod]
If you’ve used it several times, might I advise you that from now on you use…
“I am so smart. I am so smart. S-M-R-T, I mean S-M-A-R-T”
as that is the correct rendition I believe. 
Chief Wiggum: What’s so appealing about my forbidden closet of mystery?
“Ay. The hot pants.”
Capt. McAllister should have his own thread.
<The one where there’s a bachelor auction>
“Dyarrr. I’m…not attractive.”
<The one with Pinchy the lobster>
Capt. M: “Dyarr, it’s not his fault he’s a sissy. Someone’s been coddling him.”
Marge: “Don’t look at me! I wanted to eat him!”
Capt. M: “Sorry, it’s usually the mother. Ya know, I run a small academy for lobsters. We stress tough love, daily chores, and the like.”
Marge: “No! We’re not sending the lobster away to some snobby boarding school.”
McAllister: “Dyarr, I understand. It’s hard to let go. Tell me this then. Have ya got any spare change?”
<Krusty goes missing>
“Dyarr, that’s Hansome Pete. He dances for nickels. Pete! Ya got some customers!”
<Baby on board>
“Ah, squiddy. I got nothin’ against ya. I just heard there was gold in yer belly. HAR HAR HARRRRR, HAR HAR HAR HARRRR!!!”
<Burns planning a casino>
Capt. M: “I’ll need three ships, and fifty stout men. We’ll sail round the Horn and return with spices and silk, the likes of which ya have never seen.”
Burns: “You idiot - we’re building a casino!”
Capt. M: “Dyarr… can you give me five minutes?”
<Don’t remember the episodes>
“Dyarrr - I’ve got customers. Call me back, Ishmael.”
“Dyarr, and I’ve got a Tivo full of Dyarr…ma and Greg.”
Robot on fire flailing around: “Why…why was I programmed to feel pain?”
Fat Tony: “Out of ammo…let’s go to Big 5”
Monty Burns’ “Be My Vest” musical number 