Disclaimer: I define OTP my way. OTP for me does not mean the character can never ever be with anyone else, and if they are, those characters must DIE. It just means this pairing is the pairing I like most, and feel belong together in the end. And in the end, they usually do get together.
Canon? Oh yeah.
Why I like them: UST. Snark. Attitude. But they really care about each other and would do anything to save each other.
What I've Done For Them: I've explored their relationship post-ROTJ in three fanfic novels. They aren't online, though.
Canon? If you count the EU, which I do not.
Why I like them: She had enough fire to unsettle Luke and I liked that. All the other ladies in the EU just annoyed me.
What I've Done For Them: Nothing. See, Luke was too busy with my Mary Sue to care ;)
Canon? It is now.
Why I like them: They obviously liked each other, but Simon was too reserved to express himself. Their ups and downs and misunderstandings were both funny, and sad. I really loved them.
What I've Done For Them: I loved them so much that I almost wrote fanfic when the show ended. Never did.
Final Fantasy X
Type: Star-crossed, somewhat
Why I like them: I didn't at first. But as we dove deeper into the story, they grew on me. And when the inevitable was revealed, I jumped all over it. Their story became a tragic one.
What I've Done For Them: I wrote a sequel to Final Fantasy X before they made another game. I lost that story when my hard drive crashed, but it focused on Yuna dreaming of Tidus again and waking up to Rikku telling her Kilmari had found a sphere. So it basically bridged both games. I wish I still had it.
Pirates of the Caribbean
Canon? Yes, oh yes.
Why I like them: I love them. Seriously. They are one of my fave pairings ever and I have no rational way of explaining way. And At World's End? GUH.
What I've Done For Them: I have a couple of icons that I made. Sometimes I flirt with the idea of fanfic, but I just let it go.
Canon? Never quite there
Why I like them: You wouldn't think that a delivery boy from the past and a one-eyed mutant from the future would do it, but I find this pairing the most realistic pairing on TV. He's not much of a catch, but he loves her and can never express it the right way. She likes him, but he doesn't meet her unrealistic standards. It doesn't get more realistic than that.
Smallville (and other Superman related media)
Type: The stuff of legends
Canon? Future canon on SV; canon in other media
Why I like them: Lois/Clark! Probably my first OTP ever (been loving them since I was a 4) and still probably tops the list. I hate talk of destiny and fate, but this couple just fits. She is bossy and aggressive, but soft inside. He's gentler and noble, even with all his powers. Out of all the loves in his life, Lois will always be the one for Clark. And out of all the loves of her life, Clark will always be the one for her. They pretty much helped define OTP.
What I've Done For Them: Recently, I dabbled in a couple of fics for them. Nothing major.
Canon? On and off
Why I like them: I just do. Jimmy is so smitten with her and Chloe really cares for him. They have this really cute aura to them that speaks of young love. I just think it's sweet.
Canon? mild UST
Why I like them: It's weird. I never expected to like this pairing. I like Chloe/Jimmy, but it was nice to see some super-powered girl just completely crush on Jimmy. Jimmy was thrown by it because he was always trying to prove himself to Chloe, yet here is Kara who is likes him the moment she sees him. If Chloe/Jimmy doesn't work out, I wouldn't mind this pairing.
Type: UST - RST
Why I like them: Mulder/Scully is one of my fave pairings ever. Only, I wish they had never gotten together. I was one of those that wanted it in the very last episode. Instead, we got it earlier and the characters suffered from it. For me, aside from the unhealthy aspect that later became part of this pairing, I thought they were fantastic for each other. They balanced each other and completed each other.
Canon? one-sided UST
Why I like them: Because it was absolutely too cute how he fawned all over her!
Canon? Most definitely.
Why I like them: He lets her loosen up. She keeps him grounded. That's always a good combo.
Canon? Past Canon
Why I like them: He loved her so much that you can see the ache in his eyes when he talks about her. They really just never had a chance.
Technically, I don't ship for Stargate. I like the show GEN and I get antsy if it gets too shippy in the UST department. But in fandom, I've written tons and tons of pairings. Since I have written many, many pairings and feel that every pairing has something cute about it, I am so not going to list them all here. I can say something good and bad about every pairing. Obviously, I like some more than others, but if I have to draw up some hierarchy of pairings…
Let's just leave it at team=love :)
And as much as I love SPN, no ships on that show for me :)