A small heart that acts as a support for the primary heart. As well as secondary full heart. An improved ribcage that extends further to protect more vital organs, no more getting kidney punched. A larger spleen, I'd heard somewhere that might actually make our bones stronger. So let's say stronger bones too. The ability to regenerate severed limbs. That seems like a good one. Eyesight like a hawk, with the night vision of a night time predator. Improve on our jaw design so getting hit their doesn't automatically knock us out. Also a better menstrual system for women no more cramps and all that jazz. And while I'm sure some people would miss them, testicles that reside inside the body. Rather than dangling exposed. ;o