Steins;Gate is an amazing sci-fi/drama anime about time travel. It follows the story of 18-year-old Okabe Rintarou, a self-proclaimed mad scientist who refers to himself as Hououin Kyouma. He, "super hacka" Hashida Itaru, and childhood friend Shiina Mayuri comprise the Future Gadgets Lab. Quite by accident, they discover that their Future Gadget #8, the Phone Microwave (Name Subject to Change), can send text messages to the past. They start sending more messages, radically changing past events (the butterfly effect) and eventually leading to distastrous consequences....
Okabe Rintarou quotes:
"I'll say it once more. I am the mad scientist, Hououin Kyouma!"
"No one knows what the future holds. That's why its potential is infinite."
"This is the choice of Steins;Gate."
"El Psy Congroo."
And of course, the very best one...
(in heavily accented English) "Hey mister, I am mad scientist. It's so COOOOL! ... sonofabitch."
HDW stands for Hyper Dying Will in the anime/manga, Katekyo Hitman Reborn!.
It is a "mode" in which the person in that mode has internal limiters removed; that is, it releases the person's hidden awareness. Unlike Dying Will Mode, which removes external limiters and using pressure during a crisis.
Also unlike Dying Will mode, someone in HDW mode seems incredibly calm, instead of overexcited.
A Dying Will Flame appears on the forehead of the person in HDW mode. A person in HDW mode tends to have irises and pupils that match the color of the forehead flame.
Usually in Katekyo Hitman Reborn! Tsunayoshi Sawada is seen in this mode, although others have entered HDW mode as well.
Giotto/Vongola Primo, the founder of the Vongola (a mafia) Famiglia, has always been seen in HDW Mode in the KHR anime.