Earlier this month, IGN put up a video of a brand new boss fight from Dark Souls 3, which is a welcome new piece of info after seeing the same Dancer of the Frigid Valley fight from the demo over and over. It's a spoiler purely because you'll be seeing one of the bosses, and for no other reason.
There's also a bit of Murakumo action, which as far as I know is the first we've seen of it, and the player shows off its special "arts" move at about 1:35.
It looks like the HUD was intentionally disabled for this video, so you can't gather any clues from item or covenant slots, and it also keeps the name of the boss unknown. Ignore the baity headline on the IGN video, it's not the "craziest Souls boss yet" (bloody internet hyperbole), but it's still cool, and without spoiling anything, I think From is trying to create a really cool "oh crap" moment at 1:40.
Dark Souls 3, man. February is looking like a very strong month for games after all the delays from this Christmas period, so it looks like I'll have one month to get all that out of the way before this one drops in March.