Though I do believe there's no way to establish the ONE quote, I do think there many which deserve credit. Please mention the game from which the quote belongs to.

Here's first one that comes to mind and that I constantly quote in "daily life":

- "I have my contacts" - Maureen Corley - Full Throttle

Any others?

Peace is but a shadow of death
Desperate to forget it's painful past
And while we hope for promising years
After shedding a thousand tears
Yesterday's sorrow constantly nears
And while the moon still shines blue
By dawn it will turn a scarlet hue
--Kuja, FFIX

Closest thing to a Shakespearean sonnet to ever appear in a game.

.....-Gordan Freeman.

'......? - Gordan Freeman.

There just getting the preliminary out of the way.

It's time to kick ass and chew bubble gum. And I'm all out of gum

wasn't this done a couple of weeks ago?

anyway, good quotes:
"May the lord smile" "And the devil have mercy" - Killer7

"And into asylum, like a great black engine roaring to eternity. Ravaging the already benighted landscape with its savage, malevolent presence. and with, the legions of the truly damned. insanity, shear and stark. and once in human form, now gutted and torn by eons of glutted indulgence. their blood lust flecking the oily walls, living in the shrieks of victims ensnared, hanged, drawn and quartered by the serpents squalid wrythings. this is the place i have not wanted to dream of, and the dream is not the place i partly live though." - shadowman

Bulletinmybrain:
.....-Gordan Freeman.

You've just won the internet
(Is it me or is this thread awefully familiar?)

Mine so far has to be the poem LOVELESS from crisis core. Yea..less of a quote but I found it intriguing, especially how it runs parallel and foreshadows the crisis core story.

Prologue (Poem)
When the war of the beasts brings about the world's end
The goddess descends from the sky
Wings of light and dark spread afar
She guides us to bliss, her gift everlasting

Prologue (Interpreted)
When the war of the beasts brings about the world's end
The goddess descends from the sky

Wings of light and dark spread afar
She guides us to bliss, her gift everlasting

Act I (Poem)
Infinite in mystery is the gift of the goddess
We seek it thus, and take to the sky
Ripples form on the water's surface
The wandering soul knows no rest.

Act I (Interpreted)
The infinite mystery
The gift of the goddess is what the three men seek
But their fates are scattered by war

One is taken captured, one flies away
And the last becomes a hero

But the three are still bound by a solemn oath
To seek the answer together, once again

Act II (Poem)
There is no hate, only joy
For you are beloved by the goddess
Hero of the dawn, Healer of worlds

Dreams of the morrow hath the shattered soul
Pride is lost
Wings stripped away, the end is nigh

Act II (Interpreted)
Though the prisoner escapes, he is gravely wounded
His life is saved, however
By a woman of the opposing nation

He begins a life of seclusion with her
Which seems to hold the promise of eternal bliss

But as happiness grows, so does guilt
Of not fulfilling the oath to his friends

Act III (Poem)
My friend, do you fly away now?
To a world that abhors you and I?
All that awaits you is a somber morrow
No matter where the winds may blow

My friend, your desire
Is the bringer of life, the gift of the goddess

Even if the morrow is barren of promises
Nothing shall forestall my return

Act III (Interpreted)
As the war sends the world hurtling towards destruction
The prisoner departs with his newfound love
And embarks on a new journey

He is guided by hope that the gift will bring bliss
And the oath that he swore to his friends

Though no oath is shared between the lovers
In their hearts they know they will meet again

Act IV (Poem)
My friend, the fates are cruel
There are no dreams, no honor remains
The arrow has left the bow of the goddess

My soul, corrupted by vengeance
Hath endured torment, to find the end of the journey
In my own salvation
And your eternal slumber

Legend shall speak
Of sacrifice at world's end
The wind sails over the water's surface
Quietly, but surely

Act V (Poem)
Even if the morrow is barren of promises
Nothing shall forestall my return
To become the dew that quenches the land
To spare the sands, the seas, the skies
I offer thee this silent sacrifice

"Bang" - Liquid Ocelot - Metal Gear Solid 4

"This is good...isn't it..."
MGS4.

Another one-
"Fuck You!"-Travis Touchdown

Lvl 64 Klutz:
Peace is but a shadow of death
Desperate to forget it's painful past
And while we hope for promising years
After shedding a thousand tears
Yesterday's sorrow constantly nears
And while the moon still shines blue
By dawn it will turn a scarlet hue
--Kuja, FFIX

Closest thing to a Shakespearean sonnet to ever appear in a game.

I dunno, Aria di Mezzo Carattere was pretty damn poetic.

"I am a timeless chorus,
join your voice with mine
and sing victory everlasting."

That really strikes a chord with me, don't know why. Kudos if you know who says it. Maybe some more quotes will help you guess.

"Child of my enemy
why have you come?
I offer no forgiveness,
a father's sins
pass to his son."

"Do I take life or give it?
Who is victim,
and who is foe?"

Some of the Dialogues after the assassinations in Assassin's Creed were pretty cool.
"Such pride...it will destroy you child." - Tamir
"We'll see how sweet they are, the fruits of your labors. You do not free the cities as you believe, but damn them. And in the end, you'll have only yourself to blame, you who speaks of good intentions." -William of Montferrat

Also, three words; "Would You Kindly?"

Eldritch Warlord:
"I am a timeless chorus,
join your voice with mine
and sing victory everlasting."

That really strikes a chord with me, don't know why. Kudos if you know who says it. Maybe some more quotes will help you guess.

"Child of my enemy
why have you come?
I offer no forgiveness,
a father's sins
pass to his son."

"Do I take life
or give it?
Who is victim,
and who is foe?"

Gravemind in Halo 3. I feel like a fanboy now.

you exist because we allow it, and you will end because we demand it

I wonder what made these webs.

"Justice? I'd die of shame to hear the word from my own lips! Such lofty ideals cannot rule a people so common. Who has earned you the right to wield your sword of justice? To be hailed as hero? Is it not I? I, who have dirtied my hands to keep yours clean? All that you are you owe to me! You ought be on your knees thanking me, yet here you stand in judgment!"
-Dycedarg Beoulve, Final Fantasy Tactics

"Don't blame us. Blame yourself or God."
- Delita Heiral, Final Fantasy Tactics

"The reeking masses yearn for gods and miracles. It is their opiate, and they consume it greedily. The people do not endeavor towards greatness, but rather mire themselves in their petty strifes - shackles on the feet of man."
- Wiegraf Folles, Final Fantasy Tactics

"Go home and be a family man!"
- Guile, Street Fighter II

"Can't let you do that, Star Fox!"
- Wolf O'Donnell, Star Fox 64

"Surf the web, surf the web!"
- Venom, Spider-Man

And, finally...

"ULTRAAAA COMBOOOO!
- Announcer, Killer Instinct Gold

"What can change the nature of a man?"

"ur gay uninstall the game"

uber_fiend12, Call of Duty 4.

IT IS I....... Yoshimitsu...

"Would you kindly?"
-Frank Fontaine

"COME GET SOME."
-- Duke Nukem

"Do a Barrel Roll"
-Peppy Hare, StarFox 64

GET OVER HEEEEEEEEEEERE!

On LOVELESS: I love the parallel between that and the story, but you know, sometimes I was on Zack's side when he was like "SRSLY, STFU GENESIS AND GIVE ME A STRAIGHT ANSWER."

I still joined his fanclub, though.

"Builds your roofs of dead wood.
Builds your walls of dead stone.
Builds your dreams of dead thoughts.
Comes crying laughing singing back to life, takes what you steal,
And pulls the skins from your dead bones shrieking."

- Clay tablet in an abandoned Trickster temple

Thief: The Dark Project- intro to Mission 8, "The Sword"

This shall be engraved upon your soul...
Divine assault...
NIBELUNG VALESTI
(Such is your fate)

Never gets old.

Jackpot!
-Dante & Vergil

most badass moment in DMC3 ever!

Cant keep crying over every mistake,just keep trying till you run out of cake.
Portals credit song

harhol:
This shall be engraved upon your soul...
Divine assault...
NIBELUNG VALESTI
(Such is your fate)

Never gets old.

Hehe I'm playing that right now, I would love hearing her just shout out PWNED!!

its its its the way of the mountain so give me some christmas!!
--dead rising

you can't shoot me
-mgs 3

War... war never changes

Kotor 2: "You are different. When i looked at Reven it was like looking into the heart of the force, when i look at you its like looking into its death"

Too Human: "I did not lie to You" Heimdall to Baldur. "AHHHHHHHHHHHHHH" *Smashes weapon into table* Baldur's responce.

Age of Mythology: "Atlantes still has enemies, and you are needed" Athena to Arkantos

Fable 2: "My name's Hannah. Some of the townspeople call me Hammer. They think they're cleaver. They're not" Hammer to ummm You.

Warcraft 3: "Running away?, You've never fought elves before have you?" SYlvannis Windrunner (alive) to Arthas (Dead)

Oblivion: "All you have to do is insure Rupheo's death and you can join our family" Lucien Lachance to you.

Basically anything Jill or Wesker says in Umbrella Chronicles. Voice acting so bad, it's gold.

indyfan:
It's time to kick ass and chew bubble gum. And I'm all out of gum

Ive heard that before where is it from Indy?