EDIT:
The favorite thing off the top of my head falls under top secret (a public screenshot of this would break the surprise and reveal too much of a sidequest). Though theres a share of other neat things I've added that are "second to that" but they are hard to screenshot (proper RTS-like AI threat evaluation etc, target specific skill selection, self-awareness of the AI [don't hit people while you have IM on yourself OR they got thorns etc, unless there is no way out]. So a not so distant third pick is probably much of the new spell code, much of it has been screenshotted so far (Generated Items, Multiple Homing Missiles, Random Colors, Random Missiles etc).I'll make my request broad so it's up to you. What's your favorite addition that you've made (that isn't top secret right now) and can we get a screenshot if there isn't one already??