What do I buy my 18 year old male for its birthday?!?

Ok that pretty much sums up the dilemma. He's turning eighteen, lives far away, is going to be at my house for his birthday and I wont be there most of the day...school. I'm setting up a treasure hunt....eighteen year olds love those right :D
Umm but I need eighteen presents to go with each of the eighteen clues. He doesnt drink, we dont have sex (and dont intend to) annnnddd...I dunno what to get him. Any suggestions would be appreciated.

I'd get him one present but leave little clues at special places in your relationship with the last clue being a piece of whatever the present is wrapped in.