Update:
ICS L85
Steel Receiver Upper and Lower
Steel trigger guard (But that's really easy)
ICS L86 Has a Steel Bi-pod and Front lower hand guard (Terminology may be wrong)
Zamak 3 Carry Handle
Zamak 3 Cocking Handle
Zamak 3 Front Sight
Zamak 3 Flash hider
Zamak 3 Sling Mount
Aluminum Barrel (Making a barrel out of Zamak is asking for trouble)
ICS AK Series
Steel Body , Dust cover , Selector
Zamak3 Front sight, Rear sight block, Mag release and trigger Guard
And the biggest surprise for me
A&K MK46 SAW (I believe new model from A&K)
Stamped Steel Bipod legs
Stamped Steel Feed Tray
Steel Lower Frame (Including welded feed slot) This is news to me, my CA is Aluminum (Tested with Blowtorch did not melt). Typically Zamak4 melts slower than Zamak 3 and potmetal melts really quickly as they are low temperature alloys.
Steel Trigger Guard
Steel Stock Support
Steel Barrel release Lever
Steel Rear sight
Aluminum or Zamak Upper Assembly
Aluminum or Zamak Railed Handguard
Aluminum Barrel
Aluminum or Zamak Charging Handle
Aluminum or Zamak Stock tube
Aluminum or Zamak Front sight
Aluminum or Zamak Flash hider
Aluminum or Zamak Top cover
Aluminum or Zamak Gas regulator
Aluminum or Zamak Bipod Housing (So much for "Plate metal" Bipod on the Box)
RS Type 97/B
Steel Front sight
Steel Muzzle Break
Steel Barrel
Steel Carry handle including proprietary optic rail
Steel Magazine Release
Stamped Steel Mock ejection bolt
Steel Pins
Steel Trigger rod
Steel Sling mounts
Duraluminum Frame (Won't see this alot in Airsoft)
Rumor has it E&L M4 AEGs are built out of 6061 Aluminum, I emailed them and that is what they told me. But ACM companies would sell you the moon if they could :P