There are 2 major cases where Precision Spreading can be of great use: When spreading butter or cream cheese.
Cream cheese should be used for Precision Spreading training as it is the easier of the two.
Solid butter, however, is the true ultimate challenge here. As butter actually is solid as opposed to creamy.
*derp goes too fast and tears a hole in the toast because the butter is solid and just won't spread*
Dammit! I should have applied Precision Spreading there.