Which in-game events are unlockable by bringing a specific Pokémon?

As you probably know, some in-game events are unlocked if you go to a specific place while having a specific Pokémon on you or in the first party slot. What I want is a complete list of those events.

I'm mainly interested in events unlocking other Pokémon (such as the Sinjoh ruins event) and less in events unlocking items (such as the Gracidea event) or Formes (such as the Deoxys meteorites).

I know of the following:

1. Arceus unlocks the Sinjoh ruins event in HG/SS. (any one, Movie and Azure Flute can unlock it once each) -> lets you pick Dialga, Palkia or Giratina.
2. Celebi (Movie) unlocks Zorua event in B/W.
3. Raikou, Entei or Suicune (Movie, shiny) unlocks Zoroark event in B/W.
4. Regigigas (not sure where it's from, but it's Lv.100) unlocks Regi shrines in Platinum.
5. Regice, Regirock and Registeel unlock that shrine where you can get Regigigas in D/P/Pt.
6. Kyogre and Groudon (caught in HG or SS, respectively) unlock Rayquaza at the same location where the respective former Pokémon was found in HG/SS.

So, are there any more of these in Gen III+?

You already mentioned a few, and I'll be including these in my answer just for completeness and I'm pretty sure it's complete.

Diamond/Pearl

• Regigigas

  Unlocked on Snowpoint Temple (Lv 70).

  Requirement: have Regirock, Regice and Registeel in your party.

Platinum

• Regirock, Regice, Registeel

  Unlocked on Rock Peak Ruins (Route 228), Iceberg Ruins (Mt. Coronet, Route 216 near the exit) and Iron Ruins (Iron Island) respectively after obtaining the movie Regigigas.

  Requirement: have the movie Regigigas in your party.

• Regigigas

  Unlocked on Snowpoint Temple (Lv 1).

  Requirement: have Regirock, Regice and Registeel in your party.

HeartGold/SoulSilver

• Spiky-eared Pichu

  Unlocked in Ilex Forest's shrine.

  Requirement: have the Pikachu-coloured Pichu first in your party.

• Rayquaza (if that counts)

  Unlocked in Embedded Tower.

  Requirement: get the Jade Orb from Oak by showing him a Kyogre and a Groudon from HeartGold and SoulSilver respectively.

• Dialga, Palkia or Giratina

  Unlocked in Sinjoh Ruins.

  Requirement: have an event Arceus walking alongside you.

Black/White

• Zorua

  Unlocked in Game Freak building in Castelia City.

  Requirement: obtained an event obtained Celebi from a Gen IV game through PokeTransfer or Relocator.

• Zoroark

  Unlocked in Lostlorn Forest.

  Requirement: have an event shiny beast (Entei, Raikou or Suicune) from a Gen IV game through PokeTransfer or Relocator in the party.

• Terrakion and Virizion (similar to Rayquaza)

  Unlocked in Trial Chamber (Victory Road) and Rumination Field (Pinwheel Forest).

  Requirement: have captured Cobalion.

• Landorus

  Unlocked in Abundant Shrine.

  Requirement: have both Thundurus and Tornadus in party.

Black 2/White 2

• Regice and Registeel

  Unlocked in Underground Ruins.

  Requirement for Regice: Have captured Regirock and have the Iceberg Key
  Requirement for Registeel: Have captured Regirock and have the Iron Key.

• Regigigas

  Unlocked in Twist Mountain.

  Requirement: have Regirock, Regice and Registeel in party.

And there are none that I know of from Pokemon X and Y which has a condition of 'get such or such Pokemon to unlock such Pokemon' (of course, Pokemon obtained through the choice of a player, for instance those which depend on the starter picked, is not considered here as such events).

OmegaRuby/AlphaSapphire

• Regigigas

  Unlocked in Island Cave.

  Requirement: Have Regice (nicknamed it and make it hold a "cold item" such as a Casteliacone, Nevermelt Ice, Icy Rock or Snowball), Regirock and Registeel in the party. Regigigas cannot be encountered during nighttime or until after encountering Groudon/Kyogre.

• Raikou, Entei and Suicune

  Unlocked while soaring through the mirage spot Trackless Forest.

  Requirement: Have Lugia or Ho-Oh in the party. Raikou appears between HH:00 to HH:19, Entei appears between HH:20 to HH:39 and Suicune appears between HH:40 to HH:59 (HH is the hour of the day).

• Dialga or Palkia

  Unlocked while soaring.

  Requirement: Have Uxie, Mesprit and Azelf in party. Dialga appears in Alpha Sapphire and Palkia appears in Omega Ruby.

• Giratina

  Unlocked while soaring.

  Requirement: Have Palkia and Dialga in party.

• Tornadus or Thunderus

  Unlocked while soaring.

  Requirement: Have Castform in party. Thundurus appears in Alpha Sapphire and Tornadus appears in Omega Ruby.

• Landorus

  Unlocked while soaring.

  Requirement: Have Tornadus and Thunderus in party.