Normal - Female Avatar: Chrom. I thought they seemed pretty cute together, but it was kinda weird how Chrom kept calling his wife "friend", hahaha.
Hard - Male Avatar: Lissa, because she's awesome.
Lunatic - Female Avatar: Inigo, because he's my favourite. :)
I'm still on Chapter 15 of Lunatic, but on my first 2 playthroughs I beat Grima with the avatar.