Let's have a thread that goes over the pokemon in X/Y that evolve from alternate means, since there are a lot of them
Eevee evolves into Sylveon after leveling with max happiness in Pokemon Amie
Floette evolves into Florges with a dawn stone
Doublade evolves into Aegislash with a dusk stone
Skrelp evolves into Dragalge after leveling knowing camouflage
Inkay evolves into Malamar if you hold the 3ds upside down while leveling (after a certain level, need to confirm which level still)
Pancham evolves into Pangoro after leveling up with another dark type in your team

I'm sure I missed some