Happy 18th Birthday, man. Don't be an idiot like me and celebrate by going and buying a bunch of tobacco products. But if you live in the States, I do recommend going to a club with your buddies or something. Afterall, in the States there are five significant birthdays, so live it up.
16- Drivers License
18- Tobacco and the ability to do a lot more 'adult-esque' things.
25- Car Insurance goes down (My personal favourite)
65- Social Security
And wherever he may be- Happy Birthday Rez (If you happen to ever see this, yes, I remembered).