hmm...chipmusic everybody needs to have.. my picks (for albums/ep's, i'll get into musicdiscs and comps later) and in alphabetical order:
8bit - we sold our souls for nothing
alec empire aka nintendo teenage robots - we punk einheit!
alex mauer - the entire discography
bit shifter - lifes a bit shifter
bodenständig 2000 - maxi german rave blast hits 3
bokusatsu shoujo koubou - the final computer (2007)
bubblyfish - peripheral v.1.2.2
cheap dinosaurs - selftitled
c-jeff - konami
cobra laser - zx spectrum
cow'p - bass experience
disasterpeace - level AND atebite and the warring nations AND the chronicles of jammage the jam mage
dong - go square
drop da bomb - 3chnls4bit
eight bt - the 2.06 minutes man
goto80 - pretty much everything the man has done
joshua morse - waveforms
kplecraft - multi-boxer
little-scale - dynasty
minikon - minikon, super minikon
mmlworks - stereo diver 07
patric c - the horrible plans of flex busterman
rugar - my girl, the princess
red potion - der game
shnabubula - controller 1
romvelope - one course meal
virt - fx3
zan zan zawa veia - mole soul
so thats pretty much my definitive list of essentials, of course theres a lot of others, but these are the ones that have hit me the hardest.