One word: Frederick.
Man, is that guy a badass. And I paired him with Nowi, just because. Actually, it was Awkward Zombie's fault, but still.
I had Robin marry Lissa in my first playthrough, because Lissa's cute. Went with Normal/Classic, even though it's my first FE. Now I'm playing it again on Hard/Newcomer. It's quite a different experience.
Lon'qu with Lethality is about the coolest thing ever, besides the aforementioned Frederick. It's awesome when you get: 'How well will you die?' Splat! Especially if you couldn't normally have killed the target.
And characters that die in the final boss come back when you play the same save again. Saves me trying to keep them all there.
I do wish that the sound test was like the Sky Jukebox, though.