Jumping Rope (FFIX)
Dodge lightning strikes (FFX)
Celestial Weapons side quest (FFX)
Blitzball (FFX-2)
Sphere Break (FFX-2)
Calibrating lightning towers (FFX-2)

Just to name a few. Most of the mini games were annoying rather than hard. I personally find the mini games in FFX-2 to be the worst ever.