What a good Graduation Present for my 18 year old stepson??

This is a difficult position you are in. All i can really think of since you hesitate to give him money directly, is how about gift cards? He wont be able to return the items for cash, and it will actually help him buy the things he needs to make it out on his own for a little while. Little things like gas cards, maybe a grocery card, etc. I know you said he doesnt have hobbies, but everyone has something they do daily or almost every day. Does he have a favorite diner? does he work out? maybe you can pay for one of the membership months. does he occasionaly go to movies? get a gift certificate for movies and drinks/popcorn... instead of the big picture, try looking at the smaller things he likes, and do a bunch together. Wrap his favorite body wash, favorite soda, candy, food, anything in a giant basket, things you know he will use, every little bit helps someone on their own.