A selectively configurable spray gun may include a gun body comprising a selectable forward section and a rearward section. The rearward section may be connected with either of two or more selectable forward sections so as to selectively configure the spray gun to operate either with a dense phase powder supply configuration or a with dilute phase powder supply configuration. The rearward section may include a selectable powder flow path that is connectable at an inlet end to a source of dense phase powder and at an outlet end to a selectable spray nozzle in the selectable forward section that may optionally include a diffuser. An adapter may be used to connect the rearward section with a selectable spray nozzle or air cap. A manual spray gun embodiment is also presented. A selectively configurable spray gun for use with a dense phase powder supply may include a smaller diameter powder tube that extends through a larger diameter powder tube.