Answer:
Gets rid of bad ones, short and tall. Tightens when used, one size fits all.
I am free for the taking. Through all of your life, though given but once at birth. I am less than nothing in weight, but will fell the strongest of you if held.
You can only have it once you have given it.
Don't do this in the shallow end.
My first master has four legs, my second master has two. My first I serve in life, my second I serve in death. Tough I am, yet soft beside. Against ladies cheeks I often reside.
I can only be played on a windy day
Difficult
Animal
Easy
Food
Funny
Kids
Logic
What am I?