In this time of changes and misgivings, amidst all the trepidation and sometimes outright hostility brought upon by 8th edition, I thought it'd be a good idea to start a thread to remind ourselves what we love(d) about this fictional universe in the first place.
I want this thread to remain positive, so while wistfulness at the disappearance of what you loved is not minded, please don't rant. Samewise, if you dislike an opinion, you can state you disagree but please don't go beyond that. Online arguments are rarely as productive as they wish to be, especially when neither side is interested in changing their opinion.
And note that despite the title, talk about Warhammer 30,000 or Rogue Trader is welcome.
I'll start, since it's common courtesy to contribute to such a thread when you create it.
I love what I call 'the victory of entropy' in Warhammer 40,000, that is to say descendants of one person or one group getting what these same person or group believed in or preached about completely wrong. The biggest example is humanity worshiping the Emperor when he was trying to stamp out religion (whether that was sincere or a plan to indeed become the god he denied to be) and another big example is Guilliman considering his own Codex Astartes to be guidelines allowing for initiative and using one's own brain, and then most of his descendants including the Ultramarines themselves went on to treat it like dogma that can't be deviated from.
Of course, this 'victory' is not complete since Salamanders and Raven Guard still protect the weak from those who'd prey on them just to use two examples, but it's still the concept I think the most about whenever I imagine anything that resembles original fiction.