I agree with the Mercury (or winged Liberty). The draped bust is really nice, but that design is also used on other series. The Merc is unique. I also like the connection to the poet Wallace Stevens, one of my favorites. The model for the dime is supposed to have been his wife, Elsie, a great beauty of the time.
For me it's got to be the Mercury Dime. It was my favorite coin as a kid and I pulled every coin, but two, out of circulation. I was so proud of that well circulated collection. Also, I agree with Ruben that we need new coin designs, not refreshing the old ones. Bruce
I love the mercs (we don't have to be formal and say "winged liberty" do we?) except when they are really worn, like the 1919 I pulled out of circulation about six months (see avatar)... but uncirculated they are hard to beat.