Any kind of disease..children..
Not everything is worth having, even if it's free. I've been to the food bank before and they've handed me expired food, rotten food, and food that nobody even knew what it was or how to cook it because it was completely packaged in a foreign language. I pass on all of that.
Depends on what it is
i would decline many free things except if it's money, food, drinks, useful stuff, or fun & games...
a free richard simmons