What is a good birthday present for my boyfriend who's turning 18?

So my boyfriend's birthday is coming up in a week and I need some ideas of what to give him. We've been going out for almost 6 months (5 days after his birthday will be our 6 months) and I don't know how big the gift should be. He's a pacific islander who loves football, eating, singing and playing guitar, watching movies, and just having a good time. He's really into being surprised so I was thinking about having our friends help me surprise him with something big. Please help me and give me some ideas of what I can do to surprise him...or just on what to buy him. Any ideas will be helpful! MAHALO (thank you)!