Pokémon Diamond and Pearl/Sunyshore City

Sunyshore City is the home to the eighth and final gym leader, Vaulkner.

Immediately after you enter Sunyshore, you run into Flint, a member of the Elite Four. He will ask you yo give Vaulkner a challenge to try to reignite his passion for battle. You will not find Vaulkner at his gym. You must head over to the Vista Lighthouse and speak to him, before you can enter the gym.

Tasks

 * After you defeat Vaulkner, speak to Jasmin, a gym leader hailing from the Johto region, to receive HM07 (Waterfall). This task is mandatory, Waterfall is need to get to the entrance of Victory Road.
 * The Sunyshore Market, located just above the Pokémart, sells a wide variety of Poké Ball seals. Be warned though, the selection changes up every daily
 * The house in the far upper-right hand corner of the city, is home to Julie. Her husband is away at sea, and she often gets bored. Visit her daily and tell her a story, and she will attach a special ribbon to your lead Pokémon.

Sunyshore Market

 * Monday
 * Fire Seal A
 * Heart Seal A
 * Song Seal A
 * Star Seal B
 * Ele-Seal B
 * Line Seal C
 * Party Seal D
 * Tuesday
 * Fire Seal B
 * Flora Seal A
 * Heart Seal B
 * Song Seal B
 * Star Seal C
 * Ele-Seal C
 * Line Seal D
 * Wednesday
 * Fire Seal C
 * Flora Seal B
 * Heart Seal C
 * Song Seal C
 * Star Seal D
 * Ele-Seal D
 * Smoke Seal A
 * Thursday
 * Fire Seal D
 * Flora Seal C
 * Foamy Seal A
 * Heart Seal D
 * Song Seal D
 * Smoke Seal B
 * Star Seal E
 * Friday
 * Flora Seal D
 * Foamy Seal B
 * Party Seal A
 * Song Seal E
 * Heart Seal E
 * Smoke Seal C
 * Star Seal F
 * Saturday
 * Flora Seal E
 * Foamy Seal C
 * Party Seal B
 * Song Seal F
 * Heart Seal F
 * Line Seal A
 * Smoke Seal D
 * Sunday
 * Flora Seal F
 * Foamy Seal D
 * Song Seal G
 * Star Seal A
 * Ele-Seal A
 * Line Seal B
 * Party Seal C

There is also a girl who will give your Pokémon something nice if they manage to impress her with your bond and its level!

Pokémart

 * Poké Ball: [[File:Pokebuck.png]]200
 * Great Ball: [[File:Pokebuck.png]]600
 * Ultra Ball: [[File:Pokebuck.png]]1200
 * Luxury Ball: [[File:Pokebuck.png]]1000
 * Potion: [[File:Pokebuck.png]]300
 * Super Potion: [[File:Pokebuck.png]]700
 * Hyper Potion: [[File:Pokebuck.png]]1200
 * Max Potion: [[File:Pokebuck.png]]2500
 * Antidote: [[File:Pokebuck.png]]100
 * Awakening: [[File:Pokebuck.png]]250
 * Paralyz Heal: [[File:Pokebuck.png]]200
 * Burn Heal: [[File:Pokebuck.png]]250
 * Ice Heal: [[File:Pokebuck.png]]250
 * Repel: [[File:Pokebuck.png]]350
 * Super Repel: [[File:Pokebuck.png]]500
 * Max Repel: [[File:Pokebuck.png]]700
 * Escape Rope: [[File:Pokebuck.png]]550
 * Steel Mail: [[File:Pokebuck.png]]50

Gym badge #8
The eighth and final gym, you guessed it, features a complex puzzle that you must surpass to challenge the Gym Leader. The puzzle is a series of button and gear puzzles that, as you go, rise in complexity. In the first area, head onto the walkway and onto the green button. Head off of that section and onto the section you walked onto to get to the green button. Step on the next green button to move the paths again. Now you have access to the next room. In the next room, head onto the small section and repeatedly step on the blue switch until your section connects with the one next to it. Head back onto the main floor, up the flight of stairs and the newly placed bridge. Then step on the next blue switch which will connect you to the next green switch, which in turn will bring you to the other stairway and bridge set. In the next and final room, head onto the section with the red switch. After the rotations, head off the section, and onto the other and to the next switch. Head up to the next level and onto the section with the green switch. Rotate the sections until the all join together. Head over and onto the blue switch. Now, head down the newly accessed stairs and across the bridge to the first level. Now, step on the red switch, and then head back up to the second level. And, voilà, you now have access to Volkner. Volkner carries a variety of Pokémon. Use Ground-type moves to easily get his and  off your back, and any Grass-type attack to rid yourself of his. In short, you can make quick work of 75% of his Pokémon using Torterra, if you chose Turtwig as your starter. If Empoleon is your cup of tea, than you are in trouble. Though whether your starter is weak against any Volkner's Pokémon or not, you should have caught either Palkia or Dialga by this time. Instead of going to all of the trouble of strategising and finding the right Pokémon, why not just completely obliterate Volkner with your legendary?
 * Gym Leader: Volkner
 * (Lv.46)
 * (Lv.47)
 * (Lv.47)
 * (Lv.49)
 * Reward: Beacon Badge, TM57