It depends how you are going to be shooting.
If you want to do follow cams, look into a wide angle like the Tokina 11-16 f2.8. That will give you a sweet wide angle. Or, any of the Pelang/Zenitar/Bower 8mm fisheyes are good for follow cams. With video, a fisheye is a little more forgiving since your resolution is way down on what is being recorded. You dont need the sharpness of a lens you would use for stills.
Peep this: http://vimeo.com/11731571 shot by one of my buddies. The fish shots ar all the cheapo Bower fisheye on B&H.
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