AFAIK
PI1 Models A and B
The green activity LED (GPIO 16) may be written.
Pi1 Models A+ and B+
The green activity LED (GPIO 47) may be written.
The red power LED (GPIO 35) may be written.
The high USB power mode (GPIO 38) may be written.
Pi Zero and Pi Zero W
The green activity LED (GPIO 47) may be written.
Pi2
The green activity LED (GPIO 47) may be written.
The red power LED (GPIO 35) may be written.
The high USB power mode (GPIO 38) may be written.
Pi3
The green activity LED writeable via mailbox .. as GPIO 130