if he likes tanks, why not try a baneblade?
if he is cerain it needs to be metal, then one of the best models in metal for me is a unit of Grey Knight Terminators.
if he likes monster/alien type models, then either a Tyranid Carnifex of Hive Tyrant would be right up his street.
someone with more time on their hands might be able to grab the links from the
GF site for you on these three... I think images are up for those at least KMB
lol