Harold and Maude.
Damn. Nick and Nora have already been mentioned.
Guess I’ll have to go with Mickey and Mallory from Natural Born Killers.
Adam and Amanda Bonner in Adam’s Rib (1949).
Two good-looking, happily-employed lawyers (equals loads o’ cash), with no kids, in a huge Manhattan apartment way back before the Starbucks, Barnes & Noble, and The Gap invasion.
Beats Nick n’ Nora hollow, if you ask me.
Bridget Jones & Mark Darcy in Bridget Jones’ Diary
I love how he helps her cook (to rescue her from the dreadful dinner she had prepared) and how he fights Daniel for her. I also love how she chases him in her undies. 
I think Local Hero is a wonderful movie. Director Bill Forsyth has said that his script called for ‘Gordon Urquhart’ (played by Denis Lawson) and his wife (Jennifer Black) to be the ideal couple enjoying the ideal marriage, and they certainly come across that way. Something like that would suit me fine.
Heh. Of course, that ideal ain’t so hard to come by. 
And then there’s Burns and Allen…
Are you Roger Ebert?
Harry & Sally in When Harry Met Sally (coconut cake with chocolate sauce on the side)
Loretta & Ronnie in Moonstruck (“Do you love him, Loretta?” “Ma, I love him awful!”)
Roy & Pris in Bladerunner (the post-mortem kiss was oddly touching)
Hank & Leticia in Monster’s Ball (against all the odds)
Mabel (Minnie Driver) and Arthur (Rupert Everett) in An Ideal Husband. I would love to have a relationship based on incredibly witty flirtation. Too bad my life isn’t scripted by Oscar Wilde.
Crap! Can I take back my earlier one? I wanna do a “me, too” on this one.
Actually, believe it or not, this was my ideal for many years after seeing that film. I don’t know why, but I guess I’d sorta forgotten about it.
“Gotta eatcher breakfast, Margie.” Ahh, the fuzziness of it all.
Frodo Baggins, Samwise Gamgee, and Rosie Cotton. (ducking and running)
Homer and Marge in good episodes of the Simpsons.
Buster Bloodvessel and Aunt Jessie in the Beatles’ Magical Mystery Tour. Best love scene ever committed to film.
Claire and Cliff Huxtable
Diane and Lloyd in Say Anything
Paul and Jamie Bachman from “Mad About You”.
They are definately each others “Soulmate”. I refer to my soulmate as “my Jamie Bachman”… whoever she is…
Reuel
Ray Winstone and Amanda Redman in Sexy Beast.
It gets me when he tells the psychotic gangster “I lover her with all my heart!”
Charlie and Yvonne from It could happen to you. Two nice people who are happy that they have found each other, even as their worlds collapse around them.
Plus, I’m in love with Bridgit Fonda!
“I love HER with all my heart” dammit!
I suck.
Hey, Reuel_Miller said it first so I don’t have to. “Mad About You.” (And I’m pretty sure it was “Buchman,” by the way).
It’s incredibly cheesy, and I think the show deserved a lot of the mocking it got. But I have to say that there was a lot to like about the way they portrayed that marriage. They were just comfortable with each other, and still in love. You never really see that on TV or in the movies, because it’s harder to make two people who just love each other seem interesting. You’ve got to show them trying to win the other one, or trying to win them back, or cheating, or fighting with each other, or making insulting wisecracks, or taking care of the precocious kids. If we could go without that theme song, I’d be all set.
One of the episodes I remember entirely consisted of their having locked themselves in the bathroom and having to think of ways to kill time until the locksmith came. At one point, Paul suggests sex, she agrees, the scene fades out, then fades back in and Jamie says, “Okay, what now?” Something about that struck me as funnier because it was so realistic; it wasn’t the tired old Peg Bundy “done in 15 seconds again!” schtick.
And since I’ve already used up my “guy” points, I can agree with Rubystreak about Harry Burns and Sally Allbright. Something about that movie… each one of the stars, writer, and director individually makes my skin crawl, but put them all together in a romantic comedy and it just works.