Even though chances for my perfect companion are a million to one, I would hope for something like a Dremora warrior, I think that would be amazing. However, seeing as chances for that are very low, I'd go for a male Imperial Warrior who fight for the empire.
I know some of the options are a little bit limited but I tried to make it as optional as I possibly could. Also, I didn't want to put up a option for those who prefer to ride solo as this thread is mostly for those who do want to have a companion in the game.
Tell us about your perfect companion!
EDIT: One typo.