I live a few miles north of the Navy’s basic training command in Great Lakes, Illinois. A lot of the sailors refer to this area as Great Mistakes.
If New Jersey is the Armpit, and Florida is obviously the Penis, then that makes South Carolina the Pubic Hair of America.
Columbia, SC is also known as Cola.
Now: Gainesville, G-ville. In this city, last summer I lived in the area known as student ghetto… guess why? 
Now I moved a couple of blocks to the east and live just outside from student ghetto.
Back home: Río Piedras, Ciudad Universitaria.
Toronto has several local nicknames…
The Big Smoke
Tee Ohh
Tee Dot
Trannaah
Although most people who live in the “Greater Metropolitan Area” or the seperate cities which are suburbs of Toronto simply refer to it as “Downtown”.
Do you want to go Downtown? Means do you want to go into the city.
Are you being funny, there, Troy? If you use that term at a restaurant in the city make sure to look for the gob of spit in your food.
San Francisco is just called the City.
Long Beach
[ul][li]Iowa by the Sea (because of a huge influx of midwesterners in the early 20th Century)[/li][li]International City (because of the port)[/li][li]Willmore City (after its first land developer, the name changed later, obviously)[/li][li]Bahia de los Fumos (“Bay of Smokes”, named by explorer Cabrillo for brush fires or smoke signals from Signal Hill)[/ul][/li]Lakewood
[ul][li]Flakewood[/ul][/li]Sacramento:
[ul][li]Sac[/li][li]Sacto[/li][li]Sacratomato (to honor the local agriculture)[/li][li]Tree City (many nice trees here)[/li][li]River City[/li][li]Sactown[/ul][/li]San Diego
[ul][li]Blandiego[/li][li]America’s Finest City[/li][li]San Miguel (the original name or the bay, designated by explorer Cabrillo)[/ul][/li]Los Angeles
[ul][li]Smell-A[/li][li]Hell-A[/li][li]City of Angels[/li][li]Los An-gel-eeze[/ul][/li]Hawaiian Gardens
[ul][li]Hawaiian Garbage[/ul][/li]Simi Valley
[ul][li]Slimy Valley[/ul][/li]Moorpark
[ul][li]Kraproom (Moorpark backwards)[/ul][/li]National City
[ul][li]Shelltown (bullet shells, not sea shells)[/ul][/li]San Francisco
[ul][li]Frisco (abhorred by many locals)[/li][li]San Fran[/li][li]The City (preferred by many locals)[/li][li]Yerba Buena (“Good Grass” original name, before hippies)[/ul][/li]San Buenaventura
[ul]Ventura (a shorthand version so the name would fit on railroad timetables)[/ul]
Oops, I forgot a couple:
Los Angeles used to be called “El Pueblo de Nuestra Señora la Reina de los Angeles de Porciúncula” or The Town of Our Lady the Queen of Angels of the Little Portion.
Long Beach has also been called “Queen City” for the old Queen Mary ship stationed there.
“The City of Enchantment”
At least that’s what the people in charge call it. It’s not really all that enchanting. A more common nickname is “L. J.”
The Big Easy
The Crescent City
The Best Place on Earth (according to KPIX)
The Bay Area
The Peninsula (San Francisco to Sunnyvale)
East Bay (Oakland to Milpitas)
South Bay (San Jose and whatnot)
San Francisco is definitely “The City” (and Palo Alto is most certainly “Shallow Alto”)
My hometown of Toledo goes by:
[ul]
[li]The Glass City[/li][li]T-Town[/li][li]Or more recently, due to an unfortunate publicity campaign, ToleD’OH![/li][/ul]
The part of Brooklyn, NY where I live, Park Slope, is sometimes called Dyke Slope. 
Nothing special? I have always heard Southern Maryland referred to as The Land of Pleasant Living.
[SMIB voice]You got a purty mouth[/SMIB voice]
The city I live in is officially called “The City of Five Seasons”
Unofficially we like to refer to it as “The City of Five Smells”
(Quaker Oats, General Mills, Cargill, ADM [corn sweeteners] & a few others - I’m sure) you can smell it for miles.
~ The town I grew up in (also in Hawkeyeville) was called “Little Chicago” because of the drug traffic. [disclaimer] no offense to the real Chicago or anyone who lives there [disclaimer]
Hi Desert…
Apple Valley - Appleless Valley or Crapple Valley
Hesperia - Desperia
Victorville - Victimville
Adelanto - Idleanto
Lucerne Valley - None of Your Concern Valley (due to meth labs)
Phelan - Felon
The 909 - Inland Empire…
San Bernardino - San Berdoo
Fontana - Fontucky
Redlands - Deadlands
I’m from B.C., or the “Wet Coast”. Pretty accurate.
The region including my town and the next town downriver is called the Mid-Columbia. That’s particularly unoriginal, considering a larger region another 80 or 90 miles upriver (The Tri-Cities of Kennewick, Pasco and Richland, Washington) also considers itself the Mid-Columbia.
The one for my town (The Dalles, Oregon) I like dates back to the late 1950s – “The Best Little Town by a Dam Site.”
Oregon and Washington have a few classics. Tillamook, Oregon, on the Oregon Coast, is known for its brand of high quality cheese. Its slogan: “The Land of Cheese, Trees and Ocean Breeeze.”
Walla Walla, Washington used to go by “The Town So Nice, They Named It Twice.”
We’re a wild bunch, that’s for sure.
Lets see…
Was born in Hitchin which is only known as Hitchin to its residents. Its Pikeyville to everyone else.
Grew up in Stevenage which has certainly gone downhill since i left. Its now generally referred to by us ex-Stevenagers as Johnboy County because its full of little sh*ts in korn hoodies and baggy trousers who think they have something to prove.
Trips back to see my parents (who still live there) by any of their kids (We all live in various parts of London baring my 15yr old sister) are generally refered to as Johnboy Hunts.
Used to live in Twickenham (Greater London/Middlesex) which is known as Twickers (if you are a public school boy or rugby fan). To be honest we tended to call it 'Nam because of its skanky (and often violent) nightlife.
Nearby Teddington is known as (you guessed it) Teddy Town.
Also lived in Hampton Nurserylands or Legoland to its residents.
have been living in London for bloody ages now so everything outside of the city tends to go under the collective nickname The Sticks
London itself is a tricky one when it comes to nicknames.
The problem is that the area known as “London” is a huge sprawling mass of a city which doesn’t really have a nickname. Unless you are my mother in which case it is called either:
That Filth-ridden City
or
That Horrible City Which You Insist On Calling Home When It Isn’t Really Is It?! Your Real Home Is Here With Us! Why Don’t You Move Back Home?!
Generally though, it tends to be the areas themselves within London that pick up nicknames not normally the city as a whole.
So a few examples would be:
Holborn (where i work) is generally known as The Bunker due to the presence of a rather large Cold War era Nuclear Bunker Complex beneath the area.
Covent Garden (where i lunch) is simply known as The Garden.
The City of London is frequently referred to as The Square Mile. A nickname you Yanks (gawd bless ya! ) often mistakenly apply to the whole of London.
Aldwych and its surroundings are often referred to as Theaterlands
and so on.
Albuquerque is “Duke City” because it was named after a Spanish noble, the Duke of Alburquerque.
New Mexico is sometimes called the Land of Enchantment, but I’ve heard people call it the Land of Entrapment.