6th Gen has to be the generation with my second fave Pokemon introduced ever, so here's my personal faves of Kalos!
Greninja: I really love Water-type starters (duh) but none were really fast so it was nice to see a fast Water starter for once, and oh man Greninja not only looks like a badass, but it surely can act like one too thanks to its nice movepool and if you have Protean, it gets just as awesome. I really love the whole ninja theme of his evolution line.
My fave new Eeveelution and one of my top Fairy-types. There's just so many reasons why I adore Sylveon, it's cute but has the badass side to it which most cute Pokemon seem to lack. Mine was pretty much a destroyer, wrecking almost anything with his powerful Moonblast. I was glad to use him as my Fairy-type in the main story.
So yeah, we have this latest incarnation of the generic early-game butterfly but this one has a little twist to it, in that it has many different appearances (they change based on your 3DS region settings) and actually has stats to make it usable in-game. I used one early on and mine pretty much destroyed so many opponents with just Struggle Bug (I'm not joking, he was a true early sweeper) plus Compound Eyes-boosted Hurricane is something to be feared from this cute butterfly. I posted the River Vivillon pic here because that's the wing pattern I get on my game.
Possibly my new fave Psychic-type. When I saw Meowstic for the first time, I just knew I had to use one on my team and it surely didn't disappoint me. Its stats apart from Speed are claimed to be "mediocre" but with the right training it can definitely shine as a good special attacker, plus the gender differences with their level-up moves is a really nice concept. I love the female one slightly better but both are pretty cool.
I had mixed feelings towards Honedge when it was first revealed but as time grew I found out it evolves into something that can actually take a hit and also dish it out depending on the situation. I actually loved using Aegislash when I got the chance and now it's a prominent rotating team member of mine. Seriously, don't underestimate this possessed sword, it's quite the fighter and I love its unique type combination as well.
I once thought this thing was going to be another weak-as early game Electric-type but oh man was I so wrong. Heliolisk is not only fast, but is a great special attacker and can function in so many different weather conditions as well thanks to its abilities. Dry Skin is really nice since it makes him completely immune to Water moves, so I loved using mine to destroy any Water-types he was up against. And he can Surf too, which is also great if you don't have a Water-type that would normally do it.
I never usually liked some pseudo-legends, but Goodra and its evolution line are among the cutest Dragon-types ever and I was surprised at the great moves this thing learns and has the bulk to take a hit as well. While it has an annoying evolution method (natural rain seriously?) it's definitely worth it because Goodra is basically a case of badass adorable, in that it's a cute version of a normally badass type.