Let's see, Lord of the Rings (Frodo and Gandalf), Metal Gear (Snake), Star Wars (Leia, R2, Vader), Phoenix Wright, Sailor Moon (Sailor Mars), what else?
I think Sacchin is R2D2, not a Guntank. Arcueid is probably a Zeong. Saber reminds me of the robot in Disgaea 1 but there's many others in that style. Or it could be a spacesuit.