Zig Zagged with Isaac Bickerstaff: when Arcturus breaks his neck his first response is to rage pathetically against his fate, but he calms down as he slowly begins to die and apologises to his killer, resulting in this. However, when it's revealed what he did to Zee, most people lost all sympathy with him.
Attempted Rape: Heavily implied to have happened when the Imperial Guard moved in to the Tengu Stronghold. Luckily, the Commissars were there to stop both it, and the native reprisal.
The Alliance: One has been formed between the Imperium, the Tau, and some, if not all of the Gensokyo inhabitants.
All for Nothing: The Shaft of Ulysses commited suicide to terminally ram... a fake Hive ship.
Big Damn Villains: The Thousand Sons come in to save the day help drive the Tyranid's away from Youkai Mountain.
Blood Knight: Most of the Warhammer characters, although several—such as the Brotherhood of Darkness and its Daemon Prince, Gargoth—stand out.
Body Horror: What had happened to Yamame. One can only imagine what the Tyranids will do with this now tested and successful procedure.
Later side-material reveals that Yamame's genes were used to breed a new sub-species of Venomthrope Superior, which has been harassing Imperial forces in the Ultima Segmentum since the events of the roleplay.
Character Development: Eirin in particular has been through a lot by now. Being subjected to the Tyranid Hive Mind, betrayed and having one's soul trapped in a suit of Power Armour, as well gaining the attention of a Greater Daemon tends to force people to face the reality of their situation.
The Oni change as well after the attack on the Ancient City by first the Tyranids, then Nurgle.
Cold-Blooded Torture: Inquisitor Arcturus and Chapter Master Zolomon use this to get an Eldar Exarch to talk.
Cool Tank: The Dakkawagonbommawagon, a flying Baneblade with just about every type of gun ever wielded in the 40K universe to be found welded somewhere on its hull.
Good Is Not Nice: Most of the "heroic" characters from 40K qualify, but Shas'El Kai'Ro stands out. Nice chap, respectful of the natives' wishes, even planned to allow them to decide their own future rather than proselytize them. In spite of this, he has no qualms when watching Arcturus and Zolomon brutally torture an Eldar exarch, and even joins in.
Gunship Rescue: The crew of the Dakkabomma pulll one off to rescue their Mekboss.
Large Ham: The Imperials and their Chaos counterparts just love chewing scenery. Which leads to the inevitable...
Kai'Ro channels a fatal overdose of radiation in order to maroon the Deceiver in the Warp.
The Shaft Of Ulysses ramming a Hive Ship. Didn't quite work out, though.
Instant Awesome, Just Add Mecha - Youkai mountain is under attack, its taking the resident goddess everything just to hold the Tyranids back. Suddenly This starts playing and the Hisoutensoku, a giant mecha, rises out of the mountain with a green haired shrine maiden on his shoulder and charges at the Bio-Titan for a good old fashioned fist fight.
Also used against the last Tyranid Hive Ship... except it turns ou it was a decoy.
Pseudo-Reality Ensues: The inhabitants of Gensokyo normally have near god-like powers, and for the first few pages, wreak havoc on the first wave of Imperials. Then, the other factions show up, and the Imperium brings in forces reserved for fighting and killing gods...
Red Shirt: Alas, poor Generic Youkai Rabbit #231...
Upgrade Artifact: the Codex of Hakh-Kan'Tarkos, an ancient device that contains all the Eldar's knowledge of the Old Ones and can transfer this information into the brain of any sapient once activated. Turns out it's actually Marisa's Hakkero.
Useless Useful Spell: Mystia's singing can only be used to disorient and confuse people, nothing else. It helped a lot in stopping Magnus's spell to transport the planet.
Villainous Breakdown: The Deceiver freaks out when faced with the unending denizens of the Warp, a far cry from his usually calm demeanour.
Wave Motion Gun: Courtesy of the Dakkafenix/ UP YOURS FUCKFACE XXIV, used to open the way to the Empress of Rot's fortress.
Leading to a What Could Have Been: the projectile used could have been the Dakkawagon, thus delivering eleven thousand barrels of hell in the heart of the fortress.
GRAND MASTER SPARK!!
WHAM Post: The deaths of the Lunar Princesses to purge the Moon.