Wild mon using AI
Wild mon with hidden ability
Wild mon with custom ability/moves/IVs/shiny...
Flag to keep consumable items after a battle
Flags to disable some menu options (Bag, Player, Save...)
Metatile behavior for 4 way ledges (also 2 way ledges)


Show mugshots before a battle no matter then trainer class/sprite (https://www.pokecommunity.com/showthread.php?t=240183)
VAR_PRE_BATTLE_MUGSHOT_STYLE
0 One Big Bar. Full Trainer Sprites
1 One Small Bar. Half Trainer Sprites
2 Two Small Bars. Half Trainer Sprites
VAR_PRE_BATTLE_MUGSHOT_SPRITE
0 Player’s Front Picture
1 “VS” Symbol instead of Player

Check if a Key was pressed
Make key combinations show in a t-box (and check if they were correctly put)
Turbo boost (it changes main game loop afaik)
Trainer with EVs
Continue after losing vs a trainer
Generate two wild battles
Wild double grass
Change battle BG before a battle
Change battle music before a battle
Pokémon Swarms (And buffer pokémon swarm and map)
Pokémon roaming (might be a vanilla thing already) (buffer species roaming)
Items that load a custom script
Check Pokémon IVs
Check Pokémon EVs
Check Pokémon Ribbons
Check Pokémon Ball
Swap Pokémon Ball
Check Pokémon Happiness
Check Pokémon location
Check Pokémon Held Item
Change Hold Item
Check Pokémon Status
Set Ribbons
Set IVs
Add/Remove EVs
Change Happiness
Change Pokerus
Dismount Bicycle


Custom givemon Hack:
Var 0x8000: Move 1
Var 0x8001: Move 2
Var 0x8002: Move 3
Var 0x8003: Move 4
Var 0x8004: Nature
Var 0x8005: 0 if not shiny. 1 if shiny.
Var 0x8006: HP IV
Var 0x8007: Attack IV
Var 0x8008: Defense IV
Var 0x8009: Speed IV
Var 0x800A: Special Attack IV
Var 0x800B: Special Defense IV
(If the value set for one of the moves is
not a valid move (ie. 0xFFFF) the default
move will be loaded in that slot.)

Givemon with custom ball