Metaknight, Ike, and Zelda.
Metaknight is really great at keeping the pressure up but lacks a little in the finishing department.
Ike is great at finishing and dealing large amounts of damage, but several of his attacks have a pretty painful wind-up time and his run speed isn't that great.
Zelda is different than she used to be. Overall she's been toned down, but a few things were improved. In particular, I really like the new Din's Fire move. Shiek's ability to hold onto her daggers is nice too.