I have a few rules at the game table:
If I am in the middle of a game, my stuff is off limits. ALL OF IT. No, you may not see my hand, deck, or graveyard unless you are my opponent. No, my trade binder is off limits. No, my backpack stays where it is. Talk to me later.
You may use any of my dice except my Purple/Green Geminis, those are mine. I'd rather you not roll the matching D6s seperately, those are character generators, yes you may use them, no they are not cooked.
If I am not in a game, ASK before you touch anything that belongs to me. I don't care if you're my 'friend' my stuff is my stuff. Ask first.
Most of these rules are just common decency. I only ask to see cards in other people's games if I'm judging OR they have made it clear they don't mind. I never touch another players dice without permission, and in game I always ask before touching another card.