Warhammer 40k is (c) Games workshop
Dark heresy belongs to Fantasy flight games or whatever.
Yes, this shit actually happened in a Dark Heresy Game I GM.
Story: It's a combat driven campaign of Dark Heresy I run for fun with some friends. This took place on the second mission where they escaped a prison and discovered they were on a Death World. In order to reach their Inquisitor, they have to link up with a stranded acolyte who they have lost contact with. First thing one of our guardsmen does? Go sniff a flower. I gave him another chance to rescind this decision, and warned him that dicking around on a Death World is completely
Long story short, he didn't listen. Now, when the GM warns you about something... you listen. I say this because I had previously put a brain leaf frond in this particular bush while setting the game up. I told him to take an agility test; he failed and chose not to fate point it (the guy had 3 fate points in all).... and it got him. If you aren't familiar with what happens when a brainleaf attaches to your head:
Permanent -10 to Ws, Bs, T, Ag, and Per. As well as 1d10 insanity points....
So the players didn't know what to do until the NOW BRAIN LEAF THRALL got up and tried to attack them. They ripped the frond off of the guy, which immediately gave the guy an additional 3d10 insanity (bringing it up to 4d10 in all).
In the end, I chose to not make these effects permanent as they were under expensive medical care afforded by the Inquisition. But he had to play the whole mission all jacked up, and kept the insanity points.