Since we're on the topic of balls...
Here's something I've thought about a lot but for some reason never got around to posting: Ball Stretching. There are a variety of reasons men do this, but let me jump out on a limb and say it's mainly for aesthetic reasons; they want the look of low-hangers. Or, they love the idea of having free-swaying balls, the feeling of them.
But, there are guys whose balls always ride high.
It mostly has to do with the ligatures from which the nuts hang, the length of the spermatic cords, and (in some cases) the cremaster muscles. Add circumcision and, because the foreskin can't, the burgeoning cock will use the ballsac to accommodate the growing length.
Add these things up and when a guy cums, his balls (which naturally ride high and tight) can feel like they're being squeezed in a vice.
Of course, ambient temperature plays a part, too, and most guys nuts will typically be a little tight when they've got a boner.
Except under conditions of packed-in-pants heat, my boys are always high and tight. Getting a hard-on pulls them up further, cumming can damn near suck them into my body. So, I've often thought of trying to stretch out the sac so they'd hang down even when my dick is standing at full attention.
As a result, I've been researching what to use and how to use them. The best site I've found is Secret Leather. The author has put together a very informative website, explaining how to achieve your desired results based on your reasons for wanting to stretch your nutsac. Yes, he sells a leather stretching device, but he also discusses the do's and don'ts of all types; leather, metal, pumps, and homemade devices such as ropes, rubber bands, and string; he also tells you of the downside: things that can happen if you don't do this correctly.
There's more information at Wiki.
The positives are, of course, a self-image boost - particularly if you get off on parading your swaying low-hangers through locker rooms or on nude beaches, enough skin to accommodate your boner without your man-berries riding up, and more comfort and pleasure in cumming.
The worst things would be testicular torsion, or twisted testicles. This can cut off circulation to the balls and literally kill them. Next would be damaging the spermatic cords and blood vessels. Stretching them too far, too fast can cause weakened spots, or tearing. Neither is fun. Weakened spots can bulge (known as varicocele) and be painful - especially when you shoot a load. Tearing can cause leakage into the sac (known as hydrocele).
As with any attempt to alter your cock or balls, proceed with caution, so you don't end up looking like this...
Because you want to be able to enjoy them...
If you've done this I'd love to hear about the positives and negatives you experienced in attaining your goal.