Lets just start off with some of my favorite couples of the top of my head (add more later):

couple/show

NarutoxHinata -Naruto
InyuahsaxKikyo -Inyuahsa
LelouchxKallen -Code Geass
LelouchxC.C
IkkixRingo -Airgear
NatsuxErza -Fairy tail
NegeixNodoka -Mahou Sensei Negima!
NegixKū Fei
NegixChachamaru
RakixClare -Claymore
IchigoxOrihime -Bleach
RockxRevy -Black Lagoon
VincentxRe-I -Ergo proxy (if it count?)
RanmaxShampoo -Ranma 1/2
KaixMao -Blood Plus
LightxMisa -Death Note

What are yours?
Next few post I explain why i like each couple over others.