from Code Geass has a whole helmet, though he tends to use guns as opposed to a katana. Another crossplay idea is Hei
from Darker Than Black, and he has knives for weapons.
If you're a Legend of Korra fan, there's Amon, or any of the masked Equalists. (Amon is in the center, two Equalists are behind him
). That could be a lot of fun!
You could always do masked gijinkas of things like Pokemon or Portal robots, for example, if you're really set on the whole face covering. With designs like that you have some freedom to work in elements that you like