Lyn - I'm a big Fire Emblem fan and one of my disappointments with Smash is that the FE reps since Ike are too new. Lucina and Robin were fine but I don't care for Chrom or Corrin and their inclusion pretty much means that's it for FE reps. I was hoping for at least another character from an earlier game in the series or one that used a different weapon/fighting style. Yes, I know Lyn uses a sword but at least she would be a rep from a different era of the series. I always liked her character and though she'd make a good addition. Or Hector but Lyn since she's an AT.
Skull Kid - Not much more is needed.
Shovel Knight - Shovel Knight should be in more things.