Answer:
Kills the bad ones and the sad ones. Tightens to fit, so one size fits.
I am the yellow hem of the sea's blue skirt.
Half-way up the hill, I see you at last, lying beneath me with your sounds and sights. A city in the twilight, dim and vast, with smoking roofs, soft bells, and gleaming lights.
I run around the city, but I never move.
What hangs others yet can unintentionally hang itself?
I can only be played on a windy day
Difficult
Animal
Easy
Food
Funny
Kids
Logic
What am I?