I've got to say I am very excited by the increasing frequency of fairly strong Grey Knights rumours. There are lots out there and I have nothing new to add there so I won't bother to repeat them but I thought I would share why I like Chapter 666 so much. I know they aren't every one's cup of tea but I really enjoyed the Grey Knights series by Ben Counter especially the last book Hammer of Daemons. No Grey Knight has come closer to falling to Chaos than Alaric but still he stood firm.
I think the first reason is because they are shrouded in mystery. Its probably why I have latched on to Nathanial Garro's personal story in the Horus Heresy series. I believe that he is going about the task of forming the Inquisition (although of course I may be wrong, I am about a lot of things). Even the Space Marine Chapters know little about the Grey Knights.
The second is the fact that although the Space Marines are Elite the Grey Knights are more so. 1 in a 1000 may become a Space Marine, one in a million may become a Grey Knight (numbers made up). In the Killing Ground when Ventris comes up against the Grey Knight Grandmaster he is horribly over matched and I love that about them. The fact that when all things are being chucked at them the Imperium has someone else even better to throw at the depredations of the galaxy.
At the end of the day I will always be a follower of the good guys. Now I know in 40k there aren't really good guys. Even the Imperium are evil sacrificing billions to the Emperor and destroying worlds to stop their enemies from getting them and the Inquisition are certainly as bad as anyone but still there is something about the Grey Knights that just seem good and I cant wait to start a Grey Knights army.