National Gallery, Sainsbury wing. I've always liked him too, despite the fact that his anatomy is shocking. If you stood Mars up straight, he'd be a freak. I think his appeal has to do with it being simultaneously human, carnal and with a subtle, encoded non-Christian symbolism. I like Crivelli too, for his humanity and style, even though he's regarded as one of the lesser painters.
I like St. Sebastian's slightly flirty look, particularly given that he's doing his human pincushion act. And the nun who has just crept out from under St. Francis' habit.