K.C.
I don't know of a single kid named Jennifer these days. Name her that and she'll be the only one in her class - guaranteed. Go with most of the names the other posters have listed below and there will almost definitely be at least one (if not two) in the class with the same name.
At my son's school, one girl scout troop has the following children:
Ava
Ashley
Chloe
Claire
Clara
Emma
Emily
Savannah
Delaney P.
Delaney F.
(and a couple of others that weren't in any way similar to the above names but I can't remember them)
No joke - that's really how it is.