Armored Core 4 Answer, fighting White Glint.
Normally he's a bit of a ***** to fight stand up, especially for people like me who aren't exactly top notch pilots. But then he goes zipping right into the support beam of the bridge, and starts pinballing between two walls that are only about maybe fifty feet apart. With a wall on three sides out of four, I just pumped grenades and splash damaged him to death.
Never got it to happen a second time, though.
Also, any boss in FF6. Vanish + Doom/Vanish + X-Zone...it insta-gibs any boss, with only a few outstanding exceptions.