I didn't know whether to put this here, or in the 'writing' section, since we only have 2 series of the tv show.
Arguments for Lannister: Tyrion and the Lannister Song
Arguments against Lannister: Joffrey, incest and being too evil
Arguments for Stark: Sean Bean, Jon and Arya
Arguments against Stark: Lack of evil characters and Sansa being dumb
For Targaryen: Daenerys and dwaggins
Against: The mad king, and spending ages in bloody far east in the first books
Arguments for Baratheon: Renly
Against Baratheon: Stannis
Greyjoy: pay the iron price! We do not sow!
Against: Theon is pretty dumb
Martell: I dunno, I haven't go that far, yet.
I'm voting Greyjoy because I like to play them in the card game - plus they have a kraken on their crest. I almost voted for Lannister because they make the story and because of Tyrion.