dude, 16? puberty is a long on going process, and I almost guarantee you that most of your friends are not finished with it either, some get it faster than others. it just sounds like you're taking a bit longer. don't be too concerned, I am 22 and while i think I am pretty much done with it, I still notice my facial hair thickening. I really don't think I was most of the way done till i hit 20. theres a pick of me with my water polo team when i was 17, no chest hair whatsoever, and now I have tons. Hope is not lost. but I do agree with donb, just get checked out with a physician to be sure. and good luck
get a visit with a pediatric endocrinologist and they can run tests to make sure you will complete it naturally, or even give you a boost if you need it.