I don't know if this has already been documented, but anyhow here is my list:
GMST - variables of different uses TXST - texture paths MICN - menu icons GLOB - global variables? CLAS - class FACT - faction HDPT - head/face meshes? HAIR - hair meshes EYES - eyes (icons?) RACE - race (including children!) SOUN - all kinds of sounds ASPC - ambient soundscapes? MGEF - magical effects? SCPT - scripts LTEX - landscape textures? ENCH - enchantments (special effects of worn items) SPEL - spells (and bobblehead effects (since they aren't worn?)) ACTI - triggers and activators for scripts TACT - talk activators? TERM - terminals ARMO - armor BOOK - skill books CONT - containers DOOR - doors (possibly containing teleport destination by some id?) INGR - ingredients (unused) LIGH - lighting MISC - clutter items STAT - static meshes SCOL - meshes..misc MSTT - ? PWAT - pool water GRAS - grass TREE - trees FURN - furniture meshes WEAP - weapons AMMO - ammunition NPC_ - non-player characters CREA - creatures LVLC - ?? level specs of creatures? LVLN - ?? level specs of weapons? KEYM - keys ALCH - aid (food etc) IDLM - idle markers (so npc's know where they can safely play idle anims?) NOTE - notes COBJ - has no subrecords PROJ - projectiles LVLI - leveled loot lists? WTHR - weather CLMT - climate REGN - regions (of the world..?) NAVI - pathfinding nodes? CELL - interior cells WRLD - exterior cells DIAL - dialog QUST - quests IDLE - idle animations? (refers to .kf files) PACK - AI packages CSTY - combat styles LSCR - load screens ANIO - animations - other WATR - water (again?) EFSH - effect shaders EXPL - explosions DEBR - debris (gibs, actually) IMGS - image spaces (?) IMAD - ?? effects (post process?) FLST - "follow lists"? lists of stuff ... PERK - perks BPTD - body parts ADDN - unknown, some sort of weapon effects AVIF - unknown RADS - radiation levels CAMS - cameras (for VATS) CPTH - more cameras VTYP - unique NPCs IPCT - impact (decals? no strings here!) IPDS - impact data sets? ARMA - armor (again?) ECZN - encounter zones MESG - messaged probably triggered by scripts RGDL - ragdoll magic DOBJ - Default Object Manager LGTM - something templates MUSC - music!
I do hope this is useful to someone!