As a bit of a Halo fan, I just had to do this conversion. Originally I was going to use the Kasrkin Sergeant as a base, but I used an ordinary Kasrkin instead. Hours of cutting, green stuff and painting later, and there's the result. Maybe one day I'll make a small 500-1000pt Halo themed army to go with him... I already have a few Marines and two half-finished Warthogs sitting on the shelf.
WIPS here: [link]