...In no particular order.
1) James Bond and Vesper Lynd
He's a womanizing bastard and she's an ice queen. But then, despite the lack of traditional Bond Girl Slow Motion Bikini Moment they fall in love, he quits his job as super spy to marry her, then she gets killed, and he spends the rest of his life in a vengeful rampage and never loves another woman again. If I'm ever killed by an evil movie villain, that is exactly how I expect my future husband to behave. (And omfg at that scene where he licks her fingers. O. M. F. G.)
2) Isidor Straus and Ida Straus
Rose and Jack are way overrated: the real romantic couple of Titanic were Isidor and Ida Straus, you know, the old man and woman who lay embracing on their bed as the titanic sank. SO cute. That actually happened too, they were real people; Ida said she would honour her wedding pledge by staying with Isidor wherever he went. Actually maybe they shouldn't be on this list then. Whatever.
3) Lancelot and Guinevere
King Arthur's wife and his best friend fall in love and have an affair. When Arthur finds out, someone persuades him to sentence her to be burnt at the stake. But Lancelot rescues her from the burning pyre, and so Arthur goes into a war with him. Mordred (Arthur's evil brother depending on what legend you read) plots to kidnap and marry Guinevere, and take Arthur's throne. To cut a long (long, long) story short, Arthur stops him, but gets killed, and as penitence Guin spends the rest of her life as a nun, Lancelot spends his as a hermit, and they never see each other again. :(
4) Noah and Allie
From The Notebook. They fall in love and stay together their whole lives, and then they die together solely by the power of their love. Inspiring. (Future Husband, take note. Obviously I don't believe in power-of-love-induced death. Which is why when I'm married I'll be keeping a vial of cyanide in the bathroom for him. I'm thoughtful like that.)
5) Ross and Rachel
They also get the title of 'funniest couple' Even though they were so on a break, Rachel gave her job at Louis Vuitton up for him and they lived happily and hilariously ever after (in my imagination).
It's somewhat disturbing to me that most of the couples on my list end up dying, or living miserably in tragic circumstances. Obviously I have some kind of issue.
(*I would have put Romeo and Juliet on here but I am of the opinion that if they had lived, after a month or so they would have had an argument about Romeo spending too much time at the tavern or whatever, and Juliet laughing a bit too loud at Mercutio's jokes and broken up. I mean come on, they were like 14; it so wouldn't have lasted.)