New York Giants. Mostly geographic (Bronx native) and my dad's stories of their great teams of the 40s and 50s (and early 60s). Thankfully by the time I was in high school, they were an elite franchise again.
For my generation (born in the 60s), geography won't be the deciding factor. There were lots of Raiders, Dolphins, Steelers and Cowboys fans in the neighborhood because they were in the Super Bowl every year those days and on Monday Night Football. And surprisingly, those allegiances still remain. I was "weird" because I liked the Giants in the 1970s. Sprinkle in the odd Jets fan too.
Great question. Welcome to HP.