I never played the Halo games very much, only when I was at my friend's house who had it, and that was years ago. But I remember these annoying guys (barely).
About this creation
Side view. You can't really see it, but there's actually a face carved into the head. The plume on its head... well, I couldn't figure out how to make its spiky hair(?), so this was what I came up with. Its gun is a modified metal detector.