FFX - Butterfly Catcher and Lightning Dodge (you know why)
SoulCalibur III - NIGHT TERROR! (the most annoying boss I've ever encountered, along with Jinpachi)
Yakuza 2 - Marietta (the most tiring mission... and the easiest to fail, IMHO)
Metal Gear Solid 3 - The End (a bit boring/annoying) and The Fear (the non-lethal way)