Today on "I didn't know this thread existed!"/"This thread still exists?"
But seriously, Haku's Crystal Ice Mirrors are the bomb diggity to me. I love how it could be used as a psychological torture method, although, sadly, that wasn't very explored and seems like it would take a lot of chakra to maintain long enough to break someone into paranoia.
I mean, just imagine being locked in something like a room, expecting an attack at any time, and occasionally feeling your enemy brush past you into another mirror, sometimes stabbing you, sometimes slicing, sometimes just brushing to let you know they're still there, circling you. Imagine being that rat in a trap, with no feasible way out, for hours on end.
I also quite like that one iteration of Itachi's Mangekyou, I think it was, for the constant torture aspect. Similar with Gaara's Sand Coffin/Sand Burial.
I like to be a pacifist, but there's so much room in Naruto's universe for me to be absolutely demented.