Mine would be the Nemesis helix after the first inversion, that dip that then turns into the heartline twist over the station.
I've greyed out three times on that bit, and I like to sit on the left hand seats and try and reach the station when you're flipped over - it's disorientates me so much, I involuntarily shout 'WOW!' *sharp intake of breath - dazed/stunned/elated* :D:D LOVE that bit. I love the force and speed of the helix, the speed at which it looks like you'll hit the rocks and bloodfall and then suddenly, you're whipped UP and OVER, just missing the station - LOVE IT. :W
I do, I do.