Elphie, 18's fun! You can go buy lotto tickets, and go to clubs, and buy porn...if you're into that of course.
Aaaaand the most fun thing I've done since I've been 18 is sign a waiver form so that I could ride a mechanical bull. Legal adulthood can be pretty sweet.
"You can only become truly accomplished at something you love. Don't make money your goal. Instead, pursue the things you love doing, and do them so well that people can't take their eyes off you."
- Maya Angelou