Not counting MST3K: The Movie, since that will be a pretty common choice among those such as we! 
Mine are, in alphabetical order:
Airplane!
Amazon Women on the Moon
Animal Crackers
Dr Strangelove
Duck Soup
The Lost Skeleton of Cadavra
Itās a Mad Mad Mad Mad World
Monty Python and the Holy Grail
Return of the Pink Panther (really, almost any of the Pink Panther films)
Young Frankenstein
In no particular order:
National Lampoonās Vacation
National Lampoonās Christmas Vacation
The Last Lovecraft: Relic of Cthulhu
Airplane!
Meet the Hollowheads
Rock & Roll High School Forever
The Lost Skeleton of Cadavra
Bad Santa
Cannibal! The Musical
UHF
In something resembling order:
Airplane!
Young Frankenstein
The Blues Brothers
Animal House
Deadpool
Itās a Mad Mad Mad Mad World
Kingpin
Thereās Something About Mary
The Jerk
Pee Weeās Big Adventure
The General (1926, Keaton)
The Freshman (1925, Harold Lloyd)
The Navigator (1924, Keaton)
Groundhog Day (1993, Bill Murray)
The Good Fairy (1935, Wyler, Sullavan, Marshall)
Steamboat Bill Jr. (1928, Keaton)
The Apartment (1960, B. Wilder, Lemon, MacLaine)
Sullivanās Travels (1942, Preston Sturges)
The Miracle of Morganās Creek (1944, Preston Sturges)
Bringing Up Baby (1938, Hawks, Grant, Hepburn)
In no particular order:
Strange Brew
Airplane!
Pee Weeās Big Adventure
Austin Powers: International Man Of Mystery
Life Of Brian
A Shot In The Dark
The Naked Gun: From The Files Of Police Squad!
Caddyshack
Kentucky Fried Movie
Ace Ventura: Pet Detective
In no semblance of order whatsoever:
Arsenic and Old Lace
Steamboat Bill, Jr.
Monsieur Hulotās Holiday
His Girl Friday
Hopscotch
A Night at the Opera
Young Frankenstein
Hot Fuzz
The Philadelphia Story
You Canāt Take It With You
Arsenic and Old Lace
The Big Lebowski
Blazing Saddles
Caddyshack
Monty Python and the Holy Grail
O Brother, Where Art Thou?
The Princess Bride
The Producers
This Is Spinal Tap
Young Frankenstein
Honorable mentions: Being John Malkovich, The Blues Brothers, Itās a Mad Mad Mad Mad World, Men In Black, Murder By Death, The Music Man, A Night at the Opera, The Sunshine Boys, Waiting For Guffman, Wayneās World, You Canāt Cheat An Honest Man
ranked from wettest to driest
City Lights
Pee-weeās Big Adventure
Ed Wood
O Brother, Where Art Thou?
Raising Arizona
Ghostbusters
Airplane!
Young Frankenstein
National Lampoonās Christmas Vacation
Duck Soup
The Bank Dick
he didnāt make the top 10 tonight, but the Blamire oeuvre is a precious jewel
Looking over the thread, I like the Python flicks, His Girl Friday, Airplane, Young Frankenstein, Pee-Wees Big Adventure, Ghostbusters and Naked Gun - Strange Brew was fun, Dr. Strangeloveās a classic, I enjoyed Hopscotch (great cast), This is Spinal Tap and moreā¦ so many laughs on these lists.
A few others that sprung to mindā¦
Easy Living (1937, Jean Arthur was hilarious)
The Doll (1919 Ossie Oswalda, a forgotten gem)
Sherlock Jr (1924, do I adore Buster, what makes you think that? 
)
Why Worry? (1923)
The Patsy (with Marion Davies from 1929)
Better Off Dead (1985 - āI want my 2 dollars!ā)
Life Aquatic With Steve Zissou (2004)
Annie Hall (1977)
When Harry Met Sally (1989)
Bedazzled (1967)
And the list could go on and on andā¦
Gotta do this without looking at other posts first or Iāll poach stuff! 
Animal Crackers
Ghostbusters
Monty Python and the Holy Grail
Pee-Weeās Big Adventure
The Three Amigos
Whatās Up, Tiger Lily?
Murder By Death
But Iām A Cheerleader
Lock, Stock, and Two Smoking Barrels
Crazy People
And while itās very wrong of me, I unapologetically love Cats & Dogs: The Revenge Of Kitty Galore.
Looking at the other lists, I gotta add Ghostbusters and Ed Wood to my honorable mentions. Ed Wood might have made my top ten, but I wasnāt sure whether it should be primarily categorized as a comedy or not.
The In-Laws (original version)
Galaxy Quest
Universal Era Abbot & Costello films (any and all)
In chronological order:
MASH
Blazing Saddles
Monty Python and the Holy Grail
The Jerk
Airplane!
Ghostbusters
Coming to America
Groundhog Day
Anchorman: The Legend of Ron Burgandy
Shaun of the Dead
ETA: I posted my list before reviewing the thread, and I was reminded of a lot of films I missed, but I suppose those that sprang to mind immediately without cheating are going to have to do.
I canāt give that movie enough love. Thatās #1 on my (nonexistent) list.
Nice, checking the other posts there were folks with some of the same picks. And some picks I definitely would include as well, such as Galaxy Quest, Hot Fuzz, and Monsieur Hulotās Holiday.
And I missed out Mel Brooks entirely. Iād actually put High Anxiety on there for him.
Let me preface by saying I love 30s and 40s movies. Yes, I love more recent comedies, but so many really wonderful movies has been forgotten.
The More The Merrier, The Devil and Miss Jones, & Easy Living. Today when people recall Jean Arthur at all itās because of Shane. Most of her work, though, was as a genius comedic actress.
The Thin Man moviesāIāll watch and enjoy anything with William Powell and Myrna Loy.
The Lady Eve, Ball of Fire, and Christmas in Connecticut. Is there any kind of movie Barbara Stanwyck wasnāt wonderful in it? I havenāt seen it yet.
My Man Godfrey: Carole Lombard & William Powell. She died much, much too young.
Trouble in Paradise: Chances are youāve never heard of Miriam Hopkins or Kay Francis. This pre-code comedy delight will convince youāll need to see their other movies.
Blonde Crazy: Joan Blondell was never in a movie where she couldnāt steal every scene she was in. While this is more of a drama than a comedy, itās well worth watching.
His Girl Friday: Everyone knows this screwball comedy right? You donāt! OMG! Go watch it. You can thank me later.
Horse Feathers and Duck Soup: The Marx Brothers. Need I say more?
Finally, I canāt ignore Katie Hepburnās screwball comedies: The Philadelphia Story and Bringing Up Baby.
In no particular order:
Clue
Cecil B. Demented
Psycho Beach Party
Wet Hot American Summer
Mean Girls
Romy and Michelleās high school reunion
Young Frankenstein
Addams Family Values
Brain Candy (Kids in the Hall)
Four Rooms
It was very difficult to narrow this down! 
Hmm, not sure I watch that many comedies. In no particular order:
Ghostbusters
The Princess Bride
Galaxy Quest
Monty Python and the Holy Grail
Who Framed Roger Rabbit
Willy Wonka and the Chocolate Factory
The Muppet Movie
The Great Muppet Caper
Little Shop of Horrors (1986)
Airplane!
The Princess Bride
The Naked Gun
Clue
Sesame Street Presents Follow That Bird
Honorable mentions: Aladdin (the animated one, naturally), The Lego Movie, The Muppets, The Wizard of Oz, and Coco