Boston-Logan. I live near a T station here, so unless its early or late, I take the Orange Line to State and Blue Line to the Airport. It usually takes about 25 minutes from leaving my house to arriving at the terminal - competitive with Uber/taxi in any sort of traffic - and costs $2 on my Charlie Card.

I recall hearing an announcement last year that indicated that a higher percentage of passengers reach Boston-Logan by public transportation than any other airport in the United States, which isn't surprising. The airport is close to the city and well-served by public transit links, including a water taxi.