Ok, so I was just looking at old threads and found this one that immediately caught my eye, so I decided to bring the discussion back and offer my personal point of view, because I am as well obsessed about testicles, both mine and others'. I actually find them far more attractive than the dick and here's why.
In the previous comments I think there were already two important aspects, the first being that testicles are the source of masculinity and I couldn't agree more. While a penis is often regarded as the greatest symbol of male power, we all know that without the daily supply of testosterone coming from our balls, the penis wouldn't be more than a tiny and soft appendix useful only for peeing. Actually, we all start developing as females during the first stages of pregnancy and only after the Y chromosome tranforms the gonads into testosterone-producing testicles, the rest of the male reproductive structures begin to form. Later on, during puberty, the secondary sexual traits appear once again thanks to our manly balls.
The second aspect that had already been mentioned is that they are an attractive reproductive trait. We also know that it is in the testicles that sperm cells are produced and are hence the source of male fertility too. Of course bigger balls can produce larger numbers of sperm to fertilize a female, so it's no surprise that chosing male partners with big nuts would increase their chances of reproduction.
But there is a third aspect that no one has explored and I think is the reason why so many of us find the testicles so sexy. That is the psychological one. I explain. To me, the fact that testicles have such important functions results in an interesting paradox, because they are also our weakest spot, the most vulnerable part of our bodies. If you want to cause pain to a man, the most effective way is certainly kicking him in the nuts. Once again, if you'd want to eliminate reproductive competitors, it'd be quite efficient to aim at their balls once again.
So here's comes the central point of my argument. When you allow someone else to play with your testicles, you are putting yourself in a risky situation. We're not only talking about your physical integrity, but your potential offspring too (regardless of your sexual orientation, which has nothing to do with the physiological functions of the body that are the same for all of us, so save all homophobic comments). So to me that's what makes them so sexy. It is a great act of trust in each other, knowing that that person could seriously harm you without much effort, but chooses to pleasure you instead, and the same if you are the one handling someone else's.
Personally, I really llove my own, and also enjoy the sight of others', especially if they are naturally big and low hanging (I don't like to see weights or ballrings, just let them hang free, guys! That's how nature designed them). By the way, I also think that they can also be an indicator of a guy's state of mind. If he is confortable and relaxed, it is likely that they'll hang loose and low, while if he is anxious, scared or aroused, they will retract.
So, all that being said, I'd like to read what you think. Do you agree or you find it absurd?