Find a food/mineral/rare item maniac

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

Zap plate and Magnet are the same boost. Any two items that read with the same effect generally have identical effects; the reason they differ are because they have different effects on different Pokemon, usually one is an evolution item for a specific pokemon. In the case of the elemental Plates, they are actually items for Arceus to hold, they change his form and typing due to his Ability, Multitype. The Plates are probably included because there's so many it wouldn't be practical to give them all out when they eventually distribute Arceus in a gen 6 event.