Low light conditions
Ever come across a situation when the action is happening fast, light is low, place is tight, tripod won't fit in, time is less, you've got the wrong lens on and photography is imperative? WHAT DO YOU DO?
Remember, its good to get something than not get anything at all.
JACK UP YOUR ISO VALUE!!! TO THE HILT IF NEED BE.
And then, maybe in the end, you won't mind the grain even.