Twelfth Night in general is heartbreakingly romantic. Act II scene IV, when Viola agrees to woo Olivia even though she’s really in love with Orsino…is absolutely gorgeous.
“As you wish” Yelled by Wesley as he is rolling down the hill where Buttercup pushed him.
I have often thought that, in the hereafter of our lives, when I owe no more to the future and can just be a man, that we may meet, and you will come to me and claim me as yours, and know that I am your husband. It is a dream I have. King Arthur, Excalibur
She will remember your heart when men are fairy tales in books written by rabbits. Of all unicorns, she is the only one who knows what regret is - and love. Schmendrick the Magician, The Last Unicorn
From Les Liasions Dangereuses by Choderlos De Laclos:
The Chevalier Danceny to Cecile Volanges
Mademoiselle,before I yield to the pleasure (shall I say?) or the necessity of writing to you, I begin by begging you to listen to me. I feel I need your indulgence to dare the declaration of my sentiments; if I wished merely to justify them,indulgence would not be necessary. For,after all,what am I about to do but show you your own work? And what have I to say to you which has not been said before by my looks,my behavior and even my silence? And why should you be angry at a sentiment you alone caused to exist? It arose from you and doubtless is worthy of being offered to you:though it be burning as my soul,it is as pure as yours.Can it be a crime to have appreciated your charming features,your enchanting graces and that touching candor which adds an inestimable value to qualities of themselves so precious?
“Age cannot wither her, nor custom stale her infinite variety” - Shakespeare
Chicks really dig this romance shit. - Eunoia
Is it any wonder…
“And thus I clothe my naked villany
With old odd ends stolen out of holy writ;
And seem a saint, when most I play the devil.”
–Richard III, Act 1, Scene iii
**
“What is love? 'tis not hereafter;
Present mirth hath present laughter;
What’s to come is still unsure:
In delay there lies no plenty;
Then come kiss me, sweet and twenty,
Youth’s a stuff will not endure.”
–Twelfth Night, Act 2, Scene iii
[sub]Katisha is clearly becoming one of my favorite posters[/sub]
“mistress, know yourself:
down on your knees,
And thank heaven, fasting,
for a good man’s love” 
–As You Like It, Act 3, Scene V
[sub]Hey, it’s been awhile since I last used that quote[/sub]
Hah! When I saw the thread title, that was my first thought.
Fenris
Not for all markets, am I?
(But thank you for the compliment! :o ;))
As You Like It is also the source of one of the best cynical (more so out of context) quotes about love: “Men have died from time to time, and worms have eaten them, but not for love.” 
You’ve taken most of my favorites but let me add:
Romeo and Juliet
Act II scene II
“What light through yonder window breaks?
It is the east and Juliet is the sun.
Arise fair sun and kill the envious moon who is sick and pale with grief that thou her maid are far more fair than she.
Be not her maid since she is envious. Her vestal livery is sick and green and but fools do wear it. Cast it off.
It is my lady. It is my love.
Oh, that she knew she were.
She speaks, yet she says nothing. What of that?
Her eye discourses. I will answer it. I am too bold.
Tis’ not to me she speaks…”
Shakespeare and Sting:
My mistress’ eyes are nothing like the sun
My hunger for her explains everything I’ve done
No doubt. It doesn’t get any better than this.
Gosh, this is a toughie. I’ve got two selections.
1.) “Dessa, you know I know how they whipped you.'" His [Harker's] head was right by my leg and he turned and lifted my dress, kissed my thigh. Where his lips touched was like fire on fire and I trembled. It ain’t impaired you none at all,’ he said and kissed my leg again. ‘It only increase your value.’ His face was wet; he buried his head in my lap.” p. 208 from Dessa Rose by Sherley Anne Williams
2.) “Sethe,' he [Paul D] says, me and you, we got more yesterday than anybody. We need some kind of tomorrow.’
He leans over and takes her hand. With the other he touches her face. `You your own best thing, Sethe. You are.’ His holding fingers are holding hers.” p. 273 from Beloved by Toni Morrison
How about this?
“I love you, now. I’m with you, now. I’ll do my best, moment to moment, not to betray you. Now. That’s it. Nothing more. Don’t make me lie to you” - Rod’s speech from Cleansed by Sarah Kane.
She, in my opinion, wrote some of the best plays in the Nineties and had some wonderful lines about how we all crave to be loved and how violent and desperate that desire can be.