Heh. Though, most of those are just other ones. U+2776 is an exception being negative and all. The half-named U+AA51 is cute. Thanx.
All in all, the question is really if a number's opposite is 0 (negation of value) or the negative version of it (same amount, but below zero). The knee-jerk response is the opposite of 4 is -4. But, i believe it would be 0.
The poll specifically asks on 1 as it is the commonly used value in boolean types and allows for other humorous answers.