Something a little more light-hearted than family drama:
Day 21: Favorite opposites attract couple
Arthur/Gwen from Merlin - prince and peasant, arrogant and soft-spoken respectively... and yet end up complementing each other almost perfectly.
Day 22: Saddest unrequited love
Most of my couples, if not all, were ultimately requited, so this is a tough one. While I wasn't a huge shipper (the musical was barely 20 minutes), Penny/Dr. Horrible were cute, and definitely unrequited and tragic. There's just the briefest hint that she might share his feelings, but before anything can happen, Horrible's plan to defeat his do-gooder rival (who's also Penny's boyfriend) once and for all mortally wounds Penny, who dies in his arms. Not only that, her last words are about his rival. Ouch. The very end of the musical is Horrible getting what he thought he always wanted, acknowledgement as a true villain, but inwardly you can see Penny's death has broken part of him. Poor dude.
Day 23: Couple you only shipped after a long time
Harry Potter/Luna Lovegood. Luna showed up in the fifth Potter book, Order of the Phoenix, but I didn't really see her as a potential partner for Harry until the sixth book, Half-Blood Prince. Long story short, Harry was a git through most of HBP except his scenes with Luna, so I looked back at their scenes in OotP and developed a newfound appreciation for the spacey-yet-not Ravenclaw and her impact on Harry. She was able to reach him in ways no one else could, and he was never afraid to stick up for her and never afraid of being seen with her. <3
Day 24: Couple you like, but is overshadowed by another couple in a fandom
Anakin/Padmé, overshadowed by Han/Leia.
may_child pointed out in another entry that, basically, A/P is harder to root for because it's awkward and tragic, whereas H/L (aside from the star power of Harrison Ford) have that light, comedic banter that seems to more suit modern audiences. Not to say there aren't A/P fans out there - I wouldn't have been able to run an A/P site for 15 years if there weren't. They just don't get the attention. It may also be due to A/P pretty much being the new kid on the block ship-wise, barely 10-15 years ago, whereas H/L have been bickering their way to people's hearts since '77. Even Luke/Mara was around before A/P. (I think?)