Generally I'd recommend a Sturmey-Archer, but the earlier versions of their coaster brake hub had the brake actuated through the drivetrain, so you got more braking power with the hub in low gear, and less with it in high. I don't know exactly when they stopped doing that. They only work with Sturmey-Archer shifters as far as I know, but they can generally be found with 36 holes if you look.

SA hubs are the only ones you can reliably find used, at least around here.