I have a friend who bought a grey knigget codex and a korne demon codex for about two bucks apiece. Used book store.
Last night I watched "The Time Machine" (the 1960 movie) and now I am considering making Warhammer models that look like Morlocks...
Not me... Unfortunately Grey Knights missed the Rule of Cool boat, and no wonder - it’s full of Tyranids, Necrons, Fyreslayers, Tomb Kings, regular Dwarfs and Lizardmen... And if you say Grey Knights are better than Tyranids, I have one word for you: Shadowbrink.
I wasn't saying that, I was merely pointing out that no Grey Knight has fallen to chaos. Grey Knights are cool, and Tyranids are cool in a different way. I simply enjoy the coolness.