If a Rhythm Heaven character ends up happening, I think this will be the best batch of newcomers (personally speaking) ever, which is really great and funny considering people often say that these later Smash games will scrape the bottom of the barrel:
Robin - Holy god yes. The one FE character I truly wanted, and he/she plays just how I imagined. Still waiting to hear how/if weapon durability is incorporated.
Lucina - A clone of one of my favorite characters is fine by me. I was hoping maybe she'd be coupled with Chrom. Honestly Chrom being relegated to Robin's FS feels odd to me, but I'm still very satisfied about how all the Awakening stuff was handled.
Mii Fighters - Very pleased with how they were implemented. I personally want to make my Mii a Gunner. I think no Miis online is silly though. I get why, but maybe they could just make the Mii associated with your NNID playable online? And moderate which Miis can be used as avatars? That seems reasonable I think.
Palutena - Honestly I would've been happy with any new KI character because Uprising is my GOTY for 2012, but Palutena was probably my favorite. Her implementation has me curious, with all the KIU powers being her specials, but I have no doubt she'll be fun to play.
Pac-Man - The one new 3rd party (after Mega Man) I wanted and thought was fitting. I knew Sakurai would do him justice. I think with all these male/female alts, a Ms. Pac-Man alt would be amazing (I had a Ms. Pac-Man machine growing up, and if my gaming enthusiast grandfather were still around to see that he'd flip).
Greninja - Admittedly, Greninja isn't my favorite Gen 6 starter, but that's not saying too much, because all of the XY starters were great. Honestly I would've been thrilled with Chesnaught (probably my favorite Grass type ever, plus Spiky Shield would've been cool in Smash), but Greninja is still an amazing Pokemon and looks hella fun. Plus more ninjas.
Little Mac - One of the biggest "icons" I thought had been missing from Smash. I love Punch Out, and I love that they went with the Punch Out Wii design. He's just a good character.
Rosalina - Stand user, awesome. One of the best Mario character, awesome. Space goddess that commands baby stars, awesome. She's a representative from one of my favorite Mario games of all time, plus she's just a well-designed character. I love Rosalina. Plus she's my MK8 main.
Wii Fit Trainer(s) - I love the inclusion of this character. SSB4 needed a character in the vein of Game & Watch or R.O.B. and WFT is a great character to fill that role. Wacky and fun, just like I like my characters.
Mega Man - I don't have the words to describe how happy I am about Mega Man's inclusion. It's a dream come true. Thank you Sakurai.
Villager - As much as I like all the other newcomers, this is far and away my favorite. Animal Crossing is probably one of my favorite Nintendo properties, and after Sakurai's post-Brawl comments about including an AC character, I didn't have much hope. So imagine my suprise when my #1 most wanted character was the first one announced for Smash 4.