Are testicles considered symbols of power or weakest?

A little of both. The fact they they are out in harms way makes males somewhat weaker than we would otherwise be (you would think that evolution would have produced a better system).

However, it is the fact that we have them out in harms way that makes us "tough." As in we are so frigging tough that we put our own future on the line.

Depends whether someone has them by the hand and who's hand is holding them.

I agree with answers 1 (which is same as #6),2 & 3.....However as a figurative sense of things it would be more of a symbol of bravery ie: Most people wouldn't believe I had the balls (another term for testicles) to answer the question this way.

they are just a reproductive organ

both

they make men strong.

The Hindu scriptures say that Chitta (private organ) is the seat of
Prana. The word Prana means life or liveliness. Many modern scientists
tried to locate the seat of Life. Some proposed the heart to be the seat
of Life. But there are many cases that people revived to life after some
hours of stopping of the heart. Some medical experts theorized that a
body will not revive after it's brain ceases to emit the electrical
signals. Even this theory could not stand the test of truth. Modern
medicine knows that the first organ to decompose in a dead body is the
private organ. There is not single case in the medical history that a
person revived after the private organ started decomposing. Chandogya
Upanisad says (VI.5.4):

" Water when drunk becomes three fold; it's coarsest portion becomes the
urine; it's middle portion the blood, and it's subtlest portion Prana."