OH GOD I LOL'D
Girlycard is probably male, but it's unofficial. Still, "she" tends to be allowed in the yaoi and /cm/ sections, and I've seen her with a dick. Maybe she's futa. Who knows. The only reason it's unknown is because it's just Alucard, who is male, turning into a girl.
Schrodinger is male.
Heinkel is female in the pre-Hellsing short story Crossfire, but is clearly male in the main Hellsing story.
Integra is female. No question.
Walter is male.
Zorin is female, suprisingly. Hasn't appeared in this thread but she's a confusing one
Rip Van Winkle is female.
the rest are obvious