Jiralhanae. Why did it have to be Jiralhanae?
(...I think I'd rather have the Flood than them. But it's a tossup.)
Lekgolo. That's a Lekgolo (Hunter) that the Chief is staring down there. The Jiralhanae are the Brutes, which humanity doesn't really encounter until much later into the war.
Unggoy = Grunts
Sanghelli = Elites
Huragok = Engineers
Kig'Yar = Jackals
San'Shyuum = Prophets
And also, I just watched the last part of Forward Unto Dawn, and fuck me sideways - THAT WAS AMAZING.