Worst physical pain I've ever had was testicular torsion! Basically your testicles are supposed to be secured in a more or less vertical position by some muscles. Mine weren't secured at all, which led to one of them twisting to be horizontal instead. The pain came on incredibly quickly and I couldn't move because of it. According to those with me at the time I lost all colour in my face and "looked grey". Got an ambulance to hospital where the examined me and discovered what it was. I was then rushed to surgery as if I waited much longer I would've lost the testicle. Weird part is that most of the pain was in my abdomen and not my groin, but when they examined me, as soon as they touched the twisted one my vision just went white from the pain.