I had one a while ago where I was fighting a guy that reminded me of Loz from Advent Children (which kicks A Lot of ass, btw). This guy had other men coming in to help him, and I was fighting him swords to swords, while the other guys were shooting at me at the same time. Basically I was having to dodge and block sword strikes and bullets with my blade, simultaneously, like Cloud was doing in the Forest fight in Advent Children.
Then they let out a bunch of Shadow Creepers and I got over-powered, so I had to make a break for it.
Never had one with Sephiroth in it, though. Might try to incubate him, someday, and kick the shit out of him. Heh.