Seriously though, I'd have to see more of a companion before making a judgement on them.
First time I saw Donna for example I hated her, by the end though she ended up being one of my favourite Companions.
Historical, fantasy, magic, horror, supernatural, survival, vampires, demons, pirates, mutants, ghosts, romance (FxF, MxM, MxF) (Romance should be part of the plot and not the whole plot in itself), etc.
Fantasy, Magical, Romance, Dystopian, Religious, Post-Apocalyptic, Zombies (but the plot has to consist of more than just mindlessly murdering the undead), Steampunk
Urban Fantasy, High Fantasy, Epic Quest, Sci-Fi, Time Travel and World Hopping, Steampunk, Action/Adventure, Modern Drama, Mystery, Slice of Life, Romance, and many more.