I can crack my back, toes, ankles, knees, hips, elbows, knuckles, and my other finger joints besides my knuckles.
I can willingly dislocate my left shoulder and both hips, but preferably not at the same time. Even when I pull my femur from my pelvis, I can remain standing and the ball and socket joint bulges out of my side like a tumor.
I can breathe through my nose and send the air directly into my mouth, thereby creating a breeze inside my mouth. It's especially intriguing after I eat hot food and then go outside where it's cold so it's like I'm air conditioning my mouth.
I can move my tongue in a way that it vibrates the soft palate (roof of my mouth) rapidly. I can adjust the tone that it makes so I either sound like a legitimate cat purring from my throat or I can sound like plastic being bent and released.
I can create painless red and purple bruises on myself by sucking really hard on my arms (probably works other places too) while gently biting down. I haven't done this for a while because last time I did it, my mom saw the bruises and thought I was practicing self harm.
I'm pretty confident that I am nearly immune to cavities. When I was 12 or 13, I didn't brush my teeth for almost a month and never got one cavity. I'm not willing to even go a couple days anymore now because the taste in my mouth is too bad.