Funny "unofficial" Military Mottos
These "mottos" are NOT meant to offend anyone.
They are just jokes..

"The last to know and the first to be blamed"
- Communications Division

"YOU CAN TALK ABOUT US, BUT YOU CAN'T TALK WITHOUT US!"
- Signal Corps

"Truck it, or f*ck it."
or : "Nothing moves till we do"
- Transport units

While I was stationed in Misawa, Japan, a friend of mine made an unofficial unit patch for fun. In the background was a surface ship, a submarine, a spark and quill (our rate insignia), and in the foreground was a picture of a blue devil with snow and ice hanging from his horns and pitchfork. The motto around the outside of the image was - 
"NSGA Misawa - We've been to Hell... and it snows there too!"
Naval Security Group Activity, Misawa
(Thanks to Mr. Fite)

"We won't fight & you can't make us!"
USASASAD III
(US Army Security Agency Special Activities Detachment 3).
In the early 70's, I was with a small intelligence unit in PyongTaek South Korea.
The Vietnam War was still going on & most of the guys had enlisted in the
Army Security Agency specifically to avoid this SE Asian garden spot.
Although the official motto of the unit was "Vigilus Salutus" (Always Vigilant),
we adopted out own.
We also threatened to have unit patches made that had "I surrender" in several dozen foreign
languages AND braille.
(Thanks to Mr. Robinson)

"The best care anywhere"
4077 MASH (TV show)

"Nothing happens until something moves"
US Army Transportation Center.

"Muscles Are Required, Intelligence Not Essential SIR!"
MARINES

MARINE = My Ass Really Is Navy Equipment

"Uncle Sam's Misguided Children"
or
"Uncle Sam's migrating Chimpanzees"
- USMC

"DEATH FROM A BOOGIE BOARD"
ROTC Surfrider Battalion, UC Santa Barbara

"U Soldiers Aren't Ready for the Marines Yet."
"Uncle Sam Aint Released Me Yet"
U.S. ARMY
and then Spelled backwards
"Yes My Retarded Ass Signed Up."

ARMY = Aint really marines yet

"Never Again Volunteer Yourself"
NAVY

"You have to go out out. You don't have to come back."
"Support Search and Rescue, get lost"
"We who have done so much with so little for so long can now do anything with nothing."
"USCG, Uncle Sam's Confused Group"
"Under Staffed, Can't Go"
- US Coast Guard (USCG)

"When you have a Target that has to be Suppressed, Neutralized or Destroyed - Right Now!"
"You Yell, We Shell"
Unofficial Motto - Fire Support Element, 40th ID (M)

"Peace is Our Profession"
"Mass Murder is Just a Hobby"
Several different units......

"We deliver to your door"
Written on front of an IDF transport truck

"Sighted sub, glub, glub!"
US Navy Armed Guard 
(Navy gunners on WW2 merchant ships)

"You can't fly without supply"
USAF Supply troops

"Drive like Hell"
1067th Transportation Company PA Army National Guard

"You didn't see me, I wasn't there, and I'm not here now!"
U.S. Navy Communication Technicians (spooks)

"What are they gonna do?  Send us home?"
6th Communication Battalion

"If it doesn't work, paint it"
Merchant Naval Engineers

"Ubique!"
Normally means :"Everywhere"
but some have insisted that it means:
“All over the bloody place!”

"Without POL, pilots are pedestrians."
"Nobody goes until we pass them the hose."
"Without us, the world's just a static display."
USAF POL (Fuels), Air Force Fuel troops are known as POLCATs.
Nicknames: "Gas Passers"  and Painting , Odd jobs and Landscaping (POL) 

IYAAYAS! Translated: "If you ain't AMMO, you ain't sh*t!"
"We live so others may die"
USAF Munitions, Air Force Munitions troops are known as AMMO.

"Without Weapons, It's just another airline."
USAF Weapons, Air Force Weapons troops are known as Load Toads.

"We may not be the 'Pride of the Air Force,' but without us; the Pride don't Ride!"
"No Excuses! No Second Chances! If being a Vehicle Operator was fun, everyone would want to be one!"
"You're not 'Miss Daisy;' so don't call me 'driver.'"
"They have taught monkey's to fly, but they never taught them to drive!"
"Nothing happens until something moves!"
USAF Vehicle Ops, Air Force Vehicle Ops troops are known as Roadwarriors.

"Box Kickers & Label Stickers."
USAF Supply

"WITH LOVE FROM A RUBBER GLOVE"
314 MEDICAL GROUP LITTLE ROCK AFB AR

"You can talk about us, but you can't talk without us!"
"No Comm, no Bomb!"
37th Communications Squadron, Lackland Air Force Base Texas

"YAT-YAS"
"You Ain't Tracks, You Ain't Shit."
2nd Assault Amphibian Battalion

IYAOYAS
"If You Ain’t Ordnance You Ain’t Sh*t"
Marine Aviation Ordnance

"The US Coast Guard has done so much with so little for so long, that We can
do everything with nothing, forever."
US Coast Guard

"Drive it like you stole it"
Transport Units

"It takes a college education to fly it but a high school education to fix it!"
Army Aviation

"Semper Gumby"
(Always Flexible)
1-137th ASLTHB (OHARNG) unofficial motto