Exclusive to the light novels: Aureolus Izzard Made a copy of himself that had his memories and thought it was him. It goes crazy when it figures out the truth, and has the power to turn anything it hits with its dart into molten gold, even people.
Particularly during the time when Vento attacks Academy City and Aleister sends Hound Dog to retrieve Last Order.
The Agnese Forces sticking pens into their own ears and bursting their eardrums all to just stop the main effect of Index's current spell. The casual ease with which they did it really reinforces the fanatic feel of the forces and makes the danger far more real when not even basic survival instinct can stop them.
When Sister Lucia uses her "carriage wheel shrapnel attack" on Touma. The shrapnel embeds into Touma's arm, then rips itself out!
What happened to Musujime Awaki when she messed up her calculations and found part of her leg stuck in a wall, removing the leg also removed the leg's skin and muscle.
New Testament 3: Cendrillon, using magic based on "Cinderella", can remotely mutilate the feet of anyone who has feet of a different size than hers. Worse, Accelerator explains that if she had used it on him, he wouldn't have been able to block it. The spell ignores distance and obstacles to affect the target instantly, so there are no vectors for him to redirect.