John Quoteman
They are my Space Marines and they shall know no fear.
The Emperor of Mankind (Big E)
In a galaxy built on war crimes, they are the most debased war crimers of all time.
Dark Eldar (Drukhari)
Skulls for the skull throne!
Khorne
The basic weapon of an imperial guardsman
Space Vikings
Space Wolves
You forget one thing brother, it is also a hammer.
Vulkan
The boys, the lads, the _
Da Orks, WAAAAAAAAAAAAAAAAGH!
The arch traitor himself
Horus Lupercal
Bolter
Homeworld of the Salamanders
Nocturne
The time for speeches is done, The first great test is here. My order to you all is simple, yet heed it well, and exert yourselves to see it done.
They are coming. Kill them all.
A clone based society of hyper space capitalists who highly value contracts (and were totally wiped out at one point but ignore that retcon).
The squats/Leagues of Votann
This traitor legion is devoted to Tzeentch, the changer of ways.
Thousand Sons
What Orks call their guns
Shootas
What's the fastest color? (to orks)
Red uns go fastaaa!
Death is nothing compared to vindication
Konrad Curze
The oldest race/faction in the galaxy that is also the most technologically advanced
The Necrons
The most zealous chaos worshipper legion who's primarch only ever wanted the truth. Ironically his book on worshipping the Emperor is the basis for the modern Imperial Cult. (I'll take the legion name or their primarch as an answer).
The Word Bearers/Lorgar Aurelian
This weapon breaks its targets down to the atomic level, most commonly seen being wielded by Necron Warriors.
Gauss rifle/flayer
Who is the current leader of the Black Legion, herald of the Black Crusades who seeks to finish what Horus started?
Abbadon the Despoiler
Courage is fighting the kingdom which enslaves you, no matter that their armies outnumber yours by ten-thousand to one. You know nothing of courage. Honour is resisting a tyrant when all others suckle and grow fat on the hypocrisy he feeds them. You know nothing of honour.
Angron
A force that (seemingly) has the galaxy entirely surrounded, draining worlds dry before moving on to the next.
Tyranids.
The name of the greater daemon of Nurgle.
Great Unclean One.
An anti vehicle weapon employed by the Eldar
Brightlance
What was the name of the apocalyptic war between the Necrontyr (eventually Necrons), and the C'tan vs the Old ones, Eldar, and Krork?
The War in heaven