I don't think this counts as a mod, since all the guy's done is stick a Wii Remote inside a giant replica of Samus Aran's arm cannon from Metroid, but still...it means you can play Metroid Prime with a giant replica of an arm cannon.
If you think/say "but it'll get tiring", you're missing the point.
How I like to play Metroid Prime [Reddit, via Super Punch]