re: $0 balance and never missed a payment and had credit limit decreased

If you have a zero balance then closing it will not hurt you. At the very most it would be a couple of points because of your revolving credit utilization % will decrease somewhat. This is why it's important to keep even your crappy cards active. The advice earlier about buying a v-neck and paying it off is actually excellent advice.

Now that I just typed all of that a thought came to me. How old is this credit card? If it's one of your first credit cards or actually the first do NOT cancel it. It will shorten your credit history and that will impact your score.