In Pewter City's Pokémon Center, you can find a man who, once a day, will sell you a bag of Pewter Crunchies for 500P. This is the only place to get this unique item on a routine basis in the game,

By the museum in Pewter City, you'll find a woman and her Slowpoke. Once a day, she will ask you to take care of her Slowpoke while she goes to do something else. For doing so, she will give you a Big Pearl

In the various caves of the game, the Hidden Items, found by your partner Pikachu & Eevee, will respawn once a day. This means rare items like Moon Stone in Mt. Moon or Fossils in Cerulean Cave can be obtained repeatedly.

Location: Vermilion City

After getting the Chop Down Secret Technique from the captain of the S.S. Anne, the boat will leave. When you go to leave the dock, a trainer known as Mina from the Alola Region will challenge you. When defeated, she gives a Bottle Cap She can be rechallenged each day and her team improves after defeating the Elite Four.

Pokémon Trainer Mina	Jigglypuff	Mr. Mime
Battle Type Items	Level 21	Level 22
	Attacks: Sing Double Slap Disable	Attacks: Psywave Light Screen

Pokémon Trainer Mina	Mr. Mime	Wigglytuff	Ninetales
Battle Type Items	Level 54	Level 54	Level 55
	Attacks: Psychic Light Screen Reflect Dazzling Gleam	Attacks: Flamethrower Thunderbolt Shadow Ball Dazzling Gleam	Attacks: Blizzard Dazzling Gleam Dark Pulse
Rematch

As breeding is not a feature within these games and Pokémon don't have abilities, there is no easy ways to manipulate wild Pokémon natures, except by one character. In Celadon City's PokéMart, you will find Madam Celadon. For 10,000, she will ask you a question asking you which colour of flower you choose to water. This determines the dominant stat. Then, she'll ask which one you'll thin out indicating the hindered stat. She'll then tell you which nature you'll see more prominently in the wild for the rest of the day.

After you have learned the Secret Technique Strong Push, when you go to the Safari Zone Warden's house, you can push the block away to find a Diglett. Each day, this Diglett will give you a Nugget

Location: Viridian City, Pewter City, Cerulean City, Vermilion City, Celadon City, Saffron City, Fuchsia City, Cinnabar Island

After defeating the Elite Four, the Gym Leaders of Kanto, including the new Gym Leader Blue, are able to be rebattled daily. They have stronger teams than their initial battle.

Location: Kanto

After defeating the Master Trainers, you will have the ability to battle them once again each day. As always, you need to have the same Pokémon as them in order to rebattle.