Dazed and confused.
Join Date: Jul 2008
Location: Dublin, Ireland
Dark Angels have the Raven Wing and Death Wing. Death Wing fill the 1st Company role of other chapters, veterans and terminators. The Raven Wing are fast attack and reconnaissance specialists. Other than that, while in the Horus Heresy lore most legions have something unique, like the Raven Guard Shadow Masters or Salamanders pyroclasts, in the 40k lore it's really only the loyal chapters that you mentioned that have genetic flaws/upgrades that have such unique units.
Almost forgot the Black Dragons, with their bony blade like growths.