whats the best thing to give to graduating student?  

I would think any thing he can use and needs ask him if there is any thing he needs as a nurse that he might have to purchase such as a stethoscope, you could get him some thing like that, he would be using it every day and you would be remembered for your caring and generosity,

I know some nurses. They tell me that often have to work long hours and odd hours. They also tell me that enjoy being pampered. For example going on a holiday. But if that's not possible, perhaps you could also buy him some spa treats. I think that's nice too.