I'd really like this Russian amphibious 6 wheel truck with the high flotation tires. It can also be fitted with an outboard engine. Video of Arctic, off-road and water use; even the polar bear seemed to like it. . .you can even run over your buddies and not hurt them!
http://www.youtube.com/watch?v=qZ0IpUaGzs0&feature=player_embedded#at=30
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"Better is the enemy of good enough."