Grey Knight Codex:

[Khronic]

Grey Knights External Link

Gone or Changed

Inquisitorial units in Codex Inquisition
Temple Assassins now in a Dataslate
Lost Grand Master Mordrak
Lost Justicar Anval Thawn
No more The Grand Strategy (moved to Warlord Traits)
No more Psychic Pilot vehicles, except the Dreadnoughts
Crowe lost Rending
No more Psybolts
No more specialty grenades (e.g. Psychotrope and Rad, etc.)
Psycannons became Salvo weapons
Nemesis Force Swords lost +1 to Invulnerable Save
Nemesis Force Halberds went from +2 Initiative to +1 Strength, but price reduced
Nemesis Warding Stave lost the 2++ Invulnerable Save in CC, but price drastically reduced.
No more Mindstrike Missiles on Stormravens
Nemesis Doomfists are now just Power Fists (Dreadnoughts and Dreadknights)
Brotherhood Champions lost 'Herald of Titan' special rule
Nemesis Greatsword now just grants Master-crafter to the Dreadknight, but price drastically reduced.
Kaldor Draigo now just base S4 and T4
Dreadnoughts now just have regular Aegis (no more Reinforced)

LOADS of information at Blood of Kittens
Would strongly recommend a read

Grey Knights External Link