Minecraft v1.2.3_01 obfuscation
-------------------------------
(version = 1290592709000)

Granted the MCP people should beat me to having the entire thing renamed but since
I can't sleep I'm going to make this list. :) -AJ/freem

[Client]
fc -> NBTBase
gw -> NBTTagEnd
nh -> NBTTagShort
jx -> NBTTagInt
hp -> NBTTagLong
h  -> NBTTagFloat
mf -> NBTTagDouble
eo -> NBTTagByteArray
oz -> NBTTagString
lw -> NBTTagList
ip -> NBTTagCompound

pi -> IBlockAccess (? not 100% sure)
hh -> IInventory

cx -> World

dw -> Item
fo -> ItemStack

no -> Block
v  -> BlockTNT

lu -> Entity
lt -> EntityArrow
do -> EntityBoat
dp -> EntityCreeper
ga -> EntityFallingSand
az -> EntityFireball
hi -> EntityFish
pn -> EntityFX
en -> EntityItem
he -> EntityLiving
qb -> EntityMinecart
ko -> EntityPainting
ea -> EntityPlayer
bq -> EntityPlayerSP
at -> EntitySnowball
kq -> EntityTNTPrimed

fk -> EnumArt

nl -> MovementInput

mz -> Gui
bp -> GuiScreen
gg -> GuiButton
di -> GuiMainMenu

lq -> FontRenderer

[Server]
ir -> Packet
kh -> Packet0KeepAlive
ad -> Packet1Login
f  -> Packet2Handshake
h  -> Packet3Chat
gh -> Packet4UpdateTime
u  -> Packet5PlayerInventory
co -> Packet6SpawnPosition
a  -> Packet7
ed -> Packet8
az -> Packet9
hb -> Packet10Flying
ae -> Packet11PlayerPosition
gs -> Packet12PlayerLook
ef -> Packet13PlayerLookMove
ic -> Packet14BlockDig
fz -> Packet15Place
gr -> Packet16BlockItemSwitch
ff -> Packet17AddToInventory
q  -> Packet18ArmAnimation
d  -> Packet20NamedEntitySpawn
l  -> Packet21PickupSpawn
cs -> Packet22Collect
ea -> Packet23ehicleSpawn
ht -> Packet24MobSpawn
fs -> Packet28
dg -> Packet29DestroyEntity
fr -> Packet30Entity
eh -> Packet31RelEntityMove
dk -> Packet32EntityLook
bq -> Packet33RelEntityMoveLook
cr -> Packet34EntityTeleport
ho -> Packet38
s  -> Packet39
do -> Packet50PreChunk
dm -> Packet51MapChunk
ih -> Packet52MultiBlockChange
fl -> Packet53BlockChange
jf -> Packet59ComplexEntity
ju -> Packet255KickDisconnect

dx -> Entity
hn -> EntityList
dw -> EntityArrow
bg -> EntitySnowball
gj -> EntityItem
ch -> EntityPainting
jy -> EntityMob
gb -> EntityMonster
fm -> EntityCreeper
fb -> EntitySkeleton
bv -> EntitySpider
t  -> EntityGiant
gi -> EntityZombie
gd -> EntitySlime
ba -> EntityGhast
iy -> EntityPigZombie
hs -> EntityPig
cu -> EntitySheep
bf -> EntityCow
ig -> EntityChicken
cj -> EntityPrimedTNT
ib -> EntityFallingSand
jm -> EntityMinecart
fk -> EntityBoat

eo -> World

it -> IBlockAccess

he -> NBTBase
jn -> NBTTagEnd
ca -> NBTTagByte
fw -> NBTTagShort
bo -> NBTTagInt
e  -> NBTTagLong
m  -> NBTTagFloat
ei -> NBTTagDouble
gm -> NBTTagByteArray
ik -> NBTTagString
eb -> NBTTagList
v  -> NBTTagCompound