Best cough medicine around is Cough Mist by Zycam. Its homeopathic and you spray it directly in your throat. It stops coughs instantly and for 8-10 hours. Since its homeopathic, its none addictive and is safe for even younger children. I use it and my kids use it. To be sure, its tastes nasty, but it really works.
I've never tried peppermint oil or Zycam, but Vicks 44 is one of the best for me. For congestion, drinking lots of water is the best expectorant. Anything "tussin" helps, but I've read in several places that water is better.
My Grandma used to give me a cough medicine when I was little, called Buttercup syrup, I still use it now, it seems to work ok, but I probably buy it more for nostalgia than anything else, but at least it makes me feel better!
Vicks 44 always worked well for me as a kid. I haven't had many coughs as an adult, but the few times I have, Robitussin worked well.