As an iPhone owner from day one, either I'm not as klutzy as I think I am, or I live a charmed life, or I just never forget how much the iPhone costs to repair -- and consequently, have never dropped it a significant distance. Thus, I use only a standard silicon case with a lip over the front, and have done since 2007 across the three models I have owned (the original, the iPhone 4 and the iPhone 5s).
Most of them have been from Incase, so if you're looking for a case like that I'd recommend them. I did find one for my iPhone 5s from the dollar store, which is *slightly* less grippy than the previous Incase "tire-tread" design I had, but has thus far done the job. I've never used screen protectors for the iPhone, but again have not had any issues (I don't keep my iPhone in the same pocket as my keys, which seems to help).