Note: Route 22 is completely optional, so we've included it last.
Elixir - You'll spot a path blocked by a tree upon entering the route from Santalune City. Use Cut to clear the way to the item.
Super Potion - Follow the route as it wraps south, then back west. Hop the ledges to spot this item on your way back.
Tanga Berry - Use Surf from the eastern corner of the route to reach a waterfall. Descend with waterfall and hop off onto the eastern shore. Hop across the stepping stones to the south to find the Tanga Berry tree in the southeast corner of the next land section.
TM26: Earthquake - In the same area is a rock puzzle. Start by pushing the easternmost rock south four times, west four times, north twice, then west one more time to drop it into its hole. Now push the lower of the two rocks west eight times. Wrap around so you can push it north once, then push it east five times and north once to drop it into its hole. Push the final rock east five times and north three times to plug the last hole and reach the item.
Draco Plate - Use Waterfall to ascend the waterfall on the eastern edge of the area. Follow the stream to find this.
Lumiose City (Postgame)
Poke Radar - Enter the Pokemon Lab and head to the second floor. Speak to the scientist to the right to receive this.
National Pokedex - Head to Lumiose Station on North Boulevard. You'll receive this upon entering.
TMV Pass - Speak to Pokemon Professor Sycamore inside the station to receive this.
Chamber of Emptiness (Postgame)
Note: The Chamber of Emptiness can be reached by using Surf and then Waterfall along the southern edge of Route 22. The entrance is to the east.
Spooky Plate - Smack dab in the middle of the empty chamber.
Terminus Cave (Postgame)
Adamant Orb - Southwest corner of Zygarde's chamber.
Griseous Orb - Northwest corner of Zygarde's chamber.
Lustrous Orb - Southeast corner of Zygarde's chamber.
Big Nugget - Northeast corner of Zygarde's chamber. You'll have to examine the blank spot to obtain it.
Kiloude City (Postgame)
Max Revive - Upon entering Kiloude Station, speak to the boy by the train. Answer his question correctly to receive this.
Vs. Recorder - Received upon exiting the station.
TM91: Flash Cannon - Enter the far right house on the lower level of the city and head upstairs. Speak to the girl to receive this.
Nugget - Up some stairs on the east side of the city.
TM58: Skydrop - Enter the left house in the northwest section of the city. Speak to the girl at the table to receive this.