It's OK to be smart and be a musician.
Don't play with straight metric vibrato for more than 2 waves before changing color.
Don't say you can't.
Think of how sound is perceived as well as how you make it.
Flutists should be able to do 50 sit-ups; that gives you the power to play softly.
Change things in a sequence.
Go "FFFFFFFFSS" for a good cat hiss (and watch out if the cat is in the room).
Go ahead, interpret the rests.
Bring in some life by playing at a moment before the expectation.
All sounds are OK to make on the flute except that buzz, blowing like you're playing a trumpet (that desensitizes lips).