What items is he able to bring back with him?

Something I wondered throughout the show. What determines which items travel back with him? His clothes? Yes. A cell phone in his hand? Yes. But what about a person he holds hands with? Or is it only inanimate objects? What if he holds the door knob to his house? Is it only items he can carry above the ground?

I always think of random stuff like this with these types of shows. With Highlander, I always wondered what determines which cells and tissue regenerate. Hands? No. Bullet hole? Yes. Cut to the neck? No. What if you slice into 90% of his neck? Or what if you cut off the guys arms and legs and cut his upper body in half, like from the lower chest down? Is he still alive?

"Deep down I'm pretty superficial"
Ava Gardner