These are some debug cards found in saves (such as the debug Altering Cave and debug Old Sea Chart), as well as the debug option in the debug menu for Emerald, FireRed & LeafGreen and Ruby & Sapphire.
Wonder cards via Debug menu in-game
R+Start > Tamada > Wonder Card (options)
Wonder cards via sending gifts locally
Mystery Gift > Hold R while Exiting > (send cards via names)
In FRLG, option names will be in Japanese, even on a non-Japanese ROM.
These names were subsequently translated for the English debug version of Pokémon Emerald:
STAMP server 1
STAMP server 2
STAMP server 3
STAMP server 4
STAMP server 5
STAMP server 6
STAMP server 7
STAMP server 8
STAMP server 9
STAMP server 10
LINK CARD server
TRAINER distribution server
STAMP NEWS server
TRAINER NEWS server
LINK CARD NEWS server
ALTERING CAVE CARD server
RECORD NEWS test server
BAD DATA server
OLD SEA MAP CARD server (Emerald Only)
Old Sea Map [Emerald - English & Japanese]
Collect the Old Sea Map from the deliveryman
Aurora and Mystic Ticket [FireRed & LeafGreen - Every language | Emerald - English & Japanese]
Collect the tickets from the deliveryman
Note: For the FRLG ones, Wonder card text is in English, but the scripts are localized.
Egg Ticket [FireRed & LeafGreen - Every language | Emerald - English & Japanese]
Collect the egg from the deliveryman.
Egg hatches as a Pichu, with Surf.
Note: Wonder card text is in English, but the scripts are localized.
Altering Cave [FireRed & LeafGreen - English & German | Emerald - English & Japanese]
Every time you speak to the deliveryman, it changes the encounter in Altering Cave.
Note: For the FRLG ones, Wonder card text is in English, but the script is localized.
Eon Ticket [Ruby & Sapphire - All languages]
Speak to Norman in Petalburg Gym.
[We will not distribute the Debug ROMs, and it is against our rules to ask for it]