With warm regards from the Pokemon Nightmare Project team:
We combined our findings with other user's findings to get a good list of garcs 
 
List of Garcs
a\0\0\0 - DUMMY
    a\0\0\1 - DUMMY
    a\0\0\2 - DUMMY
    a\0\0\3 - DUMMY
    a\0\0\4 - DUMMY
    a\0\0\5 - DUMMY
    a\0\0\6 - DUMMY
    a\0\0\7 - DUMMY
    a\0\0\8 - DUMMY
    a\0\0\9 - DUMMY
    a\0\1\0 - DUMMY
    a\0\1\1 - WD - Move Data
    a\0\1\2 - Egg Move Map
    a\0\1\3 - Learnset (Level Up) files
    a\0\1\4 - Evolution Map
    a\0\1\5 - MEvo Map
    a\0\1\6 - 8 * 404 bytes
    a\0\1\7 - Personal Info (0x54 size)
    a\0\1\8 - 786 * 2bytes
    a\0\1\9 - Item Data
    a\0\2\0 - 921 bytes (bitflags, used sparingly - items)
    a\0\2\1 - DUMMY
    a\0\2\2 - DUMMY
    a\0\2\3 - DUMMY
    a\0\2\4 - DUMMY
    a\0\2\5 - Fonts
    a\0\2\6 - white fade anim ALYT
    a\0\2\7 - Map Fade (ALYT)
    a\0\2\8 - DUMMY
    a\0\2\9 - DUMMY
    a/0/3/0 - GameText japanese
    a/0/3/1 - GameText japanesekanji
    a/0/3/2 - GameText english
    a/0/3/3 - GameText french
    a/0/3/4 - GameText italian
    a/0/3/5 - GameText german
    a/0/3/6 - GameText spanish
    a/0/3/7 - GameText korean
    a/0/3/8 - GameText simplechinese
    a/0/3/9 - GameText traditionalchinese
    a/0/4/0 - StoryText japanese
    a/0/4/1 - StoryText japanesekanji (unused)
    a/0/4/2 - StoryText english
    a/0/4/3 - StoryText french
    a/0/4/4 - StoryText italian
    a/0/4/5 - StoryText german
    a/0/4/6 - StoryText spanish
    a/0/4/7 - StoryText korean
    a/0/4/8 - StoryText simplechinese
    a/0/4/9 - StoryText traditionalchinese
    a\0\5\0 - DUMMY
    a\0\5\1 - DUMMY
    a\0\5\2 - DUMMY
    a\0\5\3 - DUMMY
    a\0\5\4 - DUMMY
    a\0\5\5 - DUMMY
    a\0\5\6 - DUMMY
    a\0\5\7 - DUMMY
    a\0\5\8 - DUMMY
    a\0\5\9 - DUMMY
a\0\6\0 - the, An (language prefixes)
    a\0\6\1 - Item sprites
    a\0\6\2 - Pokemon sprites
    a\0\6\3 - DUMMY
    a\0\6\4 -
    a\0\6\5 -
    a\0\6\6 - Field Bag ALYT (bflim, bflan)
    a\0\6\7 - Battle UI (multilang) lower screen? (includes battle video)
    a\0\6\8 - Battle UI (multilang) upper screen sprites (primal, mega)
    a\0\6\9 - Common UI elements
    a\0\7\0 - Common UI elements ...?
    a\0\7\1 - Common UI elements ...???
    a\0\7\2 - Skybox Model
    a\0\7\3 - CSEQ/CWAR
    a\0\7\4 - Common UI Windows
    a\0\7\5 - Common UI Finger icon
    a\0\7\6 - ZONEDATA Master table
    a\0\7\7 - DUMMY
    a\0\7\8 - Battle plates
    a\0\7\9 - More UI (ribbons)
    a\0\8\0 - Battle Arena Models
    a\0\8\1 - Encounter Data (Maps) [EA - two files, day/night], NPC models, Map textures, etc
    a\0\8\2 - DUMMY
    a\0\8\3 -
    a\0\8\4 - DUMMY
    a\0\8\5 - Map Models
    a\0\8\6 - Overworld Models
    a\0\8\7 - SESD (Move Animations?)
    a\0\8\8 - DUMMY
    a\0\8\9 - DUMMY
    a\0\9\0 - MoveData part 2?
    a\0\9\1 - 47 encrypted scripts
    a\0\9\2 - 12 language (sorting?)
    a\0\9\3 - Pokémon Models
    a\0\9\4 - DUMMY
    a\0\9\5 - DUMMY
    a\0\9\6 - EdgeMap comb
    a\0\9\7 - Intro scene
    a\0\9\8 - Riding Tutorial model (ride_kenta_tut)
    a\0\9\9 - Overworld Menu buttons / rotom UI (party/trainer/options)
    a\1\0\0 - 461 bytes, bitflags?
    a\1\0\1 - 186 * trclass (20byte)
    0x02 - Ball Used
    a\1\0\2 - 8 * trdata (20byte)
    Trainer0 - Empty
    Trainer1 - Lass Ellie
    Trainer2 - Team Skull Grunt
    Trainer3 - Team Skull Admin
    Trainer4 - Youngster Honus
    Trainer5 - Rising Star Ikaika
    Trainer6 - Ace Trainer Sheri
    Trainer7 - Ace Trainer (1)
    0x00 - Trainer Class String/Model
    a\1\0\3 - 8 * trpoke (32byte/pkm)
0x00: Ability/Gender
    0x01: Nature
    0x02-0x07: EVs
    0x08-0x0B: IVs
    a\1\0\4 - DUMMY
    a\1\0\5 - Game Over
    a\1\0\6 -
    a\1\0\7 - DUMMY
    a\1\0\8 - DUMMY
    a\1\0\9 - ride effects + ???
    a\1\1\0 -
    a\1\1\1 -
    a\1\1\2 -
    a\1\1\3 -
    a\1\1\4 -
    a\1\1\5 - DUMMY
    a\1\1\6 - DUMMY
    a\1\1\7 - DUMMY
    a\1\1\8 - Window Information
    a\1\1\9 - FR Pack, SB encgrass01_anime
    a\1\2\0 -
    a\1\2\1 -
    a\1\2\2 - z-crystal sprites
    a\1\2\3 -
    a\1\2\4 -
    a\1\2\5 - DUMMY
    a\1\2\6 - DUMMY
    a\1\2\7 -
    a\1\2\8 - DUMMY
    a\1\2\9 - DUMMY
    a\1\3\0 - DUMMY
    a\1\3\1 - DUMMY
    a\1\3\2 -
    a\1\3\3 - DUMMY
    a\1\3\4 -
    a\1\3\5 -
    a\1\3\6 -
    a\1\3\7 - com_seasand02 02_beachslope
    a\1\3\8 -
    a\1\3\9 -
    a\1\4\0 - CM tr0004_00_BodyA tr0015_00_BodyA == trainer models
    a\1\4\1 -
    a\1\4\2 -
    a\1\4\3 -
    a\1\4\4 -
    a\1\4\5 -
    a\1\4\6 -
    a\1\4\7 -
    a\1\4\8 -
    a\1\4\9 -
    a\1\5\0 -
    a\1\5\1 - gfmodel situ_ride character models, tons of <10b files
    a\1\5\2 - gfmodels CDC_ba_Body, Chara_Rim_Black
    a\1\5\3 - gfmodel BattleCharacter
a\1\5\4 -
    a\1\5\5 -
    a\1\5\6 -
    a\1\5\7 -
    a\1\5\8 -
    a\1\5\9 -
    a\1\6\0 - CM p2_bottoms_dhotpants (dressup clothes model)
    a\1\6\1 -
    a\1\6\2 -
    a\1\6\3 -
    a\1\6\4 -
    a\1\6\5 - CM p2_tops_dcut (dressup clothes model)
    a\1\6\6 - CM p1_base_fi
    a\1\6\7 -
    a\1\6\8 -
    a\1\6\9 -
    a\1\7\0 -
    a\1\7\1 -
    a\1\7\2 -
    a\1\7\3 -
    a\1\7\4 -
    a\1\7\5 -
    a\1\7\6 -
    a\1\7\7 -
    a\1\7\8 -
    a\1\7\9 -
    a\1\8\0 - CM p2_face01
    a\1\8\1 - CM p2_hair_bob
    a\1\8\2 - CM p2_acceye_butterfly
    a\1\8\3 - CM p2_acchair_simplepin
    a\1\8\4 - CM p2_bag_dbag
    a\1\8\5 - CM p2_bngl_zenbress
    a\1\8\6 - CM p2_bottoms_dhotpants
    a\1\8\7 - CM p2_hat_dhat
    a\1\8\8 - CM p2_legs_short (barefoot)
    a\1\8\9 - CM p2_shoes_dshoes
    a\1\9\0 - CM p2_situ_ridesea p2_situ_ridels01_hat ...?
    a\1\9\1 - Chara_Rim_1_fi.tga
    a\1\9\2 - SMDH
    a\1\9\3 - DUMMY
    a\1\9\4 - Comb1_Manual.gffsh
    NéöxComb1_Manual
    FillScreanNéöx
    a\1\9\5 - PokeCenter heal sprites
    a\1\9\6 - DUMMY
    a\1\9\7 - overworld effects?
    ef_b_demo_uroko2_smoke
    ef_ride_apper_land
    ef_b_demo_trial2_water_splash
    a\1\9\8 - Item 1-25 popups
    a\1\9\9 - monsterball UA / UE pack gfmodel (all old pokeball models)
    a\2\0\0 - DUMMY
    a\2\0\1 - DUMMY
    a\2\0\2 - 4 ~250KB ???
    a\2\0\3 - DUMMY
    a\2\0\4 - 48 FLIM (old ribbons, scrubbed of new ones)
    a\2\0\5 - 0x44C bytes (bitflag, hardly any)
    a\2\0\6 - 25 WE pack (Environment lighting?)
    a\2\0\7 - 88 bytes
    a\2\0\8 - DUMMY
    a\2\0\9 - BG pack of Camera1
    a\2\1\0 - 11 * <80 bytes
    a\2\1\1 - 00 00 00 00 01 00 00 00 19 00 00 00 00 00 02 00 19 00 00 00 00 00 01 00 92 02 01 00 00 
00 00 00
    a\2\1\2 - FieldMenu rotom
    a\2\1\3 - DVLB drawershader version 3002 font2_RectDrawerShader
    a\2\1\4 - Forme change SPBD3
0-ea_formchange_fupa
    1-ea_formchange_gira
    2-ea_formchange_kyure
    3-ea_formchange_mitsu
    4-ea_formchange_reshi
    5-ea_formchange_syeimi
    6-ea_formchange_torne
    7-ea_formchange_zeku
    8-ea_formchange_ziga_down
    9-ea_formchange_ziga_up
    10-ea_z_bead
    a\2\1\5 - game_clear_save_dummy
    a\2\1\6 - DUMMY
    a\2\1\7 - DUMMY
    a\2\1\8 - 12 bytes: 01 00 00 00 00 00 AF C4 00 00 00 00
    a\2\1\9 - DUMMY
    a\2\2\0 - Grpfont_Finder
    a\2\2\1 - DUMMY
    a\2\2\2 - DUMMY
    a\2\2\3 - zukan picturebook
    a\2\2\4 - 4 bytes (all zeroes)
    a\2\2\5 - 4 bytes (all zeroes)
    a\2\2\6 - 4 bytes (all zeroes)
    a\2\2\7 - Release Date images
    a\2\2\8 - 27 FLIM - Available now!
    a\2\2\9 - Miracle Trade (Wonder Trade) images
    a\2\3\0 - Grpfont_FinderMenu multilang Version #
    a\2\3\1 - pokeicon_view debug
    a\2\3\2 - font_viewer debug
    a\2\3\3 - Town Map
    a\2\3\4 - Pokedex related (multiple files, 802 entries in a few)
    a\2\3\5 - 4 bytes (all zeroes)
    a\2\3\6 - THE MISTAKE
    a\2\3\7 - Pokedex language name sprites
    a\2\3\8 - Pokedex language name sprites (copy?) 
 
Clothes and Other things:  
BOY (HD) 
a176 face 
a177 hair 
a178 accessories 
a179 bag 
a180 zring 
a181 pants 
a182 hats 
a183 leg 
a184 shoes 
a185 ride outfit 
a186 shirts 
BOY (OVERWORLD) 
a202 face 
a203 hair 
a204 accessories 
a205 bag 
a206 zring 
a207 pants
a208 hats 
a209 leg 
a210 shoes 
a211 ride outfit 
a212 shirts 
GIRL (HD) 
a188 face 
a189 hair 
a190 accessories 
a191 ornaments 
a192 bag 
a193 zring 
a194 pants 
a195 hats 
a196 leg 
a197 shoes 
a198 ride outfit 
a199 shirts 
GIRL (OVERWORLD) 
a214 face 
a215 hair 
a216 accessories 
a217 ornaments 
a218 bag 
a219 zring 
a220 pants 
a221 hats 
a222 leg 
a223 shoes 
a224 ride outfit 
a225 shirts 
a098 - overworld buildings 
a094 : Pokemon 3d models 
a062 - box sprites 
a061 - item sprites 
a087 - z moves titles and Trainer battle images 
a082(a083?) - overoworld models 
a163 - some sort of 2d maps 
a174 - battle and cutscene models data/sound : all music m : moflex files containing the intro 
Pk3ds editable(tr- trainer) 
move - a\0\1\1 
eggmove - a\0\1\2 
levelup - a\0\1\3 
evolution - a\0\1\4 
megaevo - a\0\1\5 
personal - a\0\1\7 
item - a\0\1\9 
zonedata - a\0\7\7 
worlddata - a\0\9\1
 trclass - a\1\0\5 
trdata - a\1\0\6
 trpoke - a\1\0\7 e
ncounterstatic - a\1\5\9 
pickup - a\2\7\1 
maisonpkN - a\2\8\1 
maisontrN - a\2\8\2 
maisonpkS - a\2\8\3 
maisontrS - a\2\8\4 
gametext - a\0\3\2 
storytext - a\0\4\2 
encdata - a\0\8\2

Good luck everyone and have fun! 
 
-From darklink1010