Ditto. A surprisingly useful word.
I use the “Coolness, sir” variant. Man, what a good show that was.
From Arrested Development: “Has anyone in this family ever even SEEN a chicken?”
From Futurama: “What’s the good of Science if nobody gets hurt?!”
Reminds me of a favorite: “Timmmaaayy”
Big fan here of Foghorn Leghorn’s “Sharp as a bag of wet mice” (for displays of underwhelming intellectual acuity)
And Ralph’s “Me fail English? That’s unpossible!” (for any disaster)
Ooh, and Homer’s line upon shooting himself in the butt with an air rifle “Not the good cheek!” (for any self inflicted disaster)
Hahaha, I use the bag of wet mice too. Also a fan of “about as subtle as a hand grenade in a barrel of oatmeal.”
I also use a variation on this, when calling ahead before going somewhere, explaining that I don’t want to “Land like a rock in a bowl of oatmeal.” The visual is pretty good that people never seem annoyed that I’m calling to ask annoying questions after that. 
“Oh yeah? Well, the Jerk Store called, and they’re all out of YOU!”
From Seinfeld, when someone is being a jerk.
More Seinfeldisms include:
“Serenity Now!”
“It’s the summer of George!”, when someone told me this year was going to be a great summer.
From SouthPark:
“Jewbots! Flame On!” said just this week, when someone was exagerating what they did on a job.
The Simpsons:
“Eeexcellent”
“Release the hounds”
“Or what? You’ll release the dogs? Or the bees? Or the dogs with bees in their mouths, and when they bark they shoot bees at you?”
“mmmmmm… forbidden donut”
not a sitcom, but “I don’t think that word means what you think it means” Inigo Montoya of The Princess Bride.
“Settle down, Beavis!”
“Huh, huh, you said ‘hole’, uh huh, huh.” (substitute any other halfway suggestive word for ‘hole’)
And from South Park, when someone asks how I’m doing:
[Big Gay Al] I’m SUPER! Thanks for asking!" [/Big Gay Al]
One I just picked up this weekend from Top Gear.
When something breaks, “Ooh that sounded expensive.”
I use Homer’s “I are smart! S-M-R-T!” when I’m wrong.
Thankfully that doesn’t happen very often.
Liz’beth!.. Comin’ to join ya, honey!
Pow! Straight to the moon!
Hellllllo ball!
I got a note.
Bob! B-O-B-E – Bob! Chrisse!
Hardly a catch phrase, but my favorite sit-com lines: “Oh, Andy! You’re not going to punish the boy!?” Snick (as Andy lights a cigarette): “Fraid I may hafto, Aint Bee.”
A great deal of my working stock phrases come from Looney Tunes:
Bugs Bunny
What a maroon
Of course you realize this means war
Yais?
Daffy Duck
I’m not like other people. I don’t like pain. It hurts me.
I would like … I would like a trip to Europe. (when asked which of several options I prefer)
also
“Very in-ter-est-ing” - Laugh-In
when responding this way via email I sometimes paste in a picture of Artie Johnson in costume
P.S. I’m so glad to find a group where people remember Parker Lewis Can’t Lose.
“Can it peel an apple?” when confronted with any new technology or process.
Kiss my grits.
I want to go to there.
Speaking of Timmys, whenever someone gets killed on a tv show I either say
“Oh my god, they killed X” (South Park)
or
“We’re gonna need another X!” (Dinosaurs)
Also from Dinosaurs, whenever my baby brother would cry when being held my someone other than Mom, I would say “Not the Mama!”
I use a lot of these. One that I have to explain to my boyfriend every time I say it and I wish he would just learn it or ignore it already is;
[Ralphie] Yay, sleep is where I’m a viking! [/Ralphie]
I came in here to mention that one. Only, I"m pretty sure it’s “You shot who in the what now?”
I don’t think so, Twickster.
(Al…and just about everybody, actually…on Home Improvement)
“Missed it by that much” from Get Smart.
Lots of Firesign Theatre, especially
“He’s no fun, he fell right over” when I knock over a chair or something.
Whenever my wife fumbles her words I usually say, “Thanks, Pan” (The Office reference)
A lot already mentioned, but off the top of my head…
“Eeexcelent!” - (Mr. Burns, The Simpsons)
“Same thing we do every night; plot to take over the world” - (Pinky and the Brain)
“I must have taken a wrong turn in Albuquerque” - (Bugs Bunny)
“Hmmm… Isn’t it lovely!” - (Marvin the Martian)
“Where’s the kaboom?” - (Marvin the Martian)
“Yoiks! And away!” - (Daffy Duck, Robin Hood Daffy)
“Missed it by that much!” (Maxwell Smart, Get Smart)
“I see NOTHING!” or “I hear NOTHING!” - (Sgt. Schultz, Hogan’s Heros)
“Humor. It is a difficult concept.” - (Spock, Star Trek) (OK, not a sitcom, but still…)
“Mmmm… Smell that oxygen!” - (From a radio play)