What should I buy my son for his 18th birthday?

My son is 18 in a couple of months. In Australia, that is the age young people come of age. He can legally vote, drink and do anything he wants (that is legal) without parental permission.

He wants a new cologne and I am giving him an almost new TV for his room but I want to get him something that will mark this day for the special day it is. Something he can keep forever as a memento from his parents of him reaching maturity. I suggested a watch, or an identity bracelet or some other piece of jewellery. I thought of a first edition of a book he loves. I ran some of these ideas past him and he just looked at me without any glee. So, any ideas?

I don’t like the idea of hip flasks/tankards and other drinking vessels because frankly, I don’t think young people need any motivation to drink and I want to instil in him the knowledge that he can actually say no to alcohol. So what else could I buy him that is symbolic but doesn’t cost an arm and a leg? I bought a guitar for his sister and put towards my other daughter’s first car… he doesn’t drive and much to my regret is choosing not to play an instrument (although he has a lot of talent).