I'm going to be short on the text this time. Shoddy Battle correctly demonstrates ingame limitations on possible IV/nature combinations on legendaries and Pokemon with XD or Pokemon Box moves. Here's what's possible for those searching.
Perfect IV possible natures: Modest, Timid, Lax, Naive, Rash, Calm, Careful, Hardy, Docile
Modest Hidden Powers that work by default: Fighting, Ground, Flying, Dark
HP Fire with modest: 31/26/31/30/30/31
HP Water with modest: 31/19/31/30/30/31
HP Electric with modest: 31/11/31/31/30/31
HP Grass with modest: 31/02/31/31/30/31
HP Ice with modest: 27/30/30/31/31/31 OR 31/10/30/31/31/31
HP Poison with modest: 31/03/30/31/30/30
HP Psychic with modest: 31/26/31/30/31/31
HP Bug with modest: 31/19/31/30/31/30
HP Rock with modest: 31/03/30/30/31/30
HP Ghost with modest: 31/31/30/31/31/26 OR 27/31/30/31/31/30 OR 31/15/26/31/31/30
HP Dragon with modest: 31/02/31/31/31/31
HP Steel with modest: 31/03/31/31/31/30
Timid Hidden Powers that work by default: Water, Electric, Grass, Ice, Poison, Ground, Bug, Rock, Dark
HP Fire with timid: 31/18/31/30/30/31
HP Fighting with timid: 31/03/30/30/30/30
HP Flying with timid: 31/03/31/30/30/30
HP Psychic with timid: 31/10/31/30/31/31
HP Ghost with timid: 31/11/30/31/31/30
HP Dragon with timid: 31/02/31/31/31/31
HP Steel with timid: 31/03/31/31/31/30
Mild Hidden Powers that work by default: Fire, Psychic, Bug, Steel
HP Ice with Mild: 31/26/30/31/31/31
I'll probably update later, but this should satisfy most people's needs. Eventually we can make this into a complete database to make sure no one ever has to calculate Hidden Power IVs.
Perfect IV possible natures: Modest, Timid, Lax, Naive, Rash, Calm, Careful, Hardy, Docile
Modest Hidden Powers that work by default: Fighting, Ground, Flying, Dark
HP Fire with modest: 31/26/31/30/30/31
HP Water with modest: 31/19/31/30/30/31
HP Electric with modest: 31/11/31/31/30/31
HP Grass with modest: 31/02/31/31/30/31
HP Ice with modest: 27/30/30/31/31/31 OR 31/10/30/31/31/31
HP Poison with modest: 31/03/30/31/30/30
HP Psychic with modest: 31/26/31/30/31/31
HP Bug with modest: 31/19/31/30/31/30
HP Rock with modest: 31/03/30/30/31/30
HP Ghost with modest: 31/31/30/31/31/26 OR 27/31/30/31/31/30 OR 31/15/26/31/31/30
HP Dragon with modest: 31/02/31/31/31/31
HP Steel with modest: 31/03/31/31/31/30
Timid Hidden Powers that work by default: Water, Electric, Grass, Ice, Poison, Ground, Bug, Rock, Dark
HP Fire with timid: 31/18/31/30/30/31
HP Fighting with timid: 31/03/30/30/30/30
HP Flying with timid: 31/03/31/30/30/30
HP Psychic with timid: 31/10/31/30/31/31
HP Ghost with timid: 31/11/30/31/31/30
HP Dragon with timid: 31/02/31/31/31/31
HP Steel with timid: 31/03/31/31/31/30
Mild Hidden Powers that work by default: Fire, Psychic, Bug, Steel
HP Ice with Mild: 31/26/30/31/31/31
I'll probably update later, but this should satisfy most people's needs. Eventually we can make this into a complete database to make sure no one ever has to calculate Hidden Power IVs.