Where are the NPC Pokemon traders that I can trade with, and what do they offer?

Question

Every Pokemon game features NPCs that you can trade with in order to obtain different Pokemon, and Pokemon X and Y are no different.

I usually try and find and trade with all the NPC traders throughout a game. However so far I've only found one in Santalune City (he wants a Bunnelby for a Farfetch'd named Quacklin' - the best name ever, IMHO).

So where are all the other NPC traders? What Pokemon do they want, and what do they offer in exchange?

Answer 1

So far that I've found, the in-game trades are as follows:

• Bunnelby -> Farfetch'd: Santalune City (House, West from the fountain)
  • Jolly
• Jigglypuff -> Bisharp: Snowbelle City (House, Southwest of the northern bridge)
  • Adamant
• Luvdisc -> Steelix: Cyllage City (Pokemon Center)
  • Impish
• Gyarados -> Magikarp: Random hotel (Must talk to a Hiker repeatedly over the course of a few days)
  • Adamant
• Any Pokemon -> Eevee: Random hotel (Must talk to a woman repeatedly over the course of a few days)
  • Docile and holds a Rare Candy

After Elite Four

• Any Pokemon -> Starter: Vaniville Town (outside your house)
  • You will get the starter yours is strongest against.
• Any Pokemon -> Ralts: Lumiose City, (Cafe Soleil on Southern Boulevard)
  • Comes with Gardevoirite