I, personally, like all of them (although the King of Red Lions is a bit iffy for some reason). Favorite's gotta go to Midna, because I love her character. She just sorta comes alive with all her rude and snappy remarks. Navi, like everyone says, is rather annoying with all her auto-tune sounding, "Hey! Listen!", but I'm kinda fond of her now. Tatl was like Midna, only on a lesser scale. Fi is my second favorite, simply because she's not a tsundere like Midna is, but she's like her own version of one. She's this rather emotionless robot-like being with artificial intelligence (I'm not too sure about that, I'm about halfway through the game! But I've read spoilers, of course -_____-) and in the end, shows some emotion. And of course that's rather heartwarming for me.