Mine is Rikka and Yuuta from Chuunibyou demo Koi ga Shitai! They're not actually a couple, but I like their relationship especially how Yuuta threat her. FINALLY! (You'll understand what I meant once you started watching Chu-2)
and...
I'VE SEEN THIS BEFORE. TEEHEE~ XD
Also Victorique and Kujo from Gosick. They've been through a hard time, and yet, they've never forgotten each other even when the World is at War.