Probably the Cardinals because they were the lovable losers of the old NFC before they were the lovable losers of the new NFC. Hard not to root for an underdog, and two decent seasons aside, they've been the underdog every year.
I also like the Packers (strong Seahawks ties plus one of my better friends is a Packers fan from Wisconsin), Patriots (Tom Brady is awesome, Belichick is a character), Broncos (love Peyton Manning and have tons of friends who are Bronco fans from Colorado), Titans (Locker), Jaguars (Bradley plus I still remember the Brunell days), Dolphins (GM has issues, but I like a lot of the players he's drafted, it's a team that is rising despite his incompetence in other areas) and Saints (Brees, Payton, Loomis (Loomis has strong Seahawks ties) are all class acts and all very good at what they do). I guess I'm starting to like the Bengals too. They've drafted very well in recent years and they are basically the closest thing the AFC has to offer in terms of having a Seahawks type team that is young, physical, and on the upswing.