Though most Buttercups are of the bovine persuasian, this humble flower name was given to the lovely princess in "The PrincessBride." If Buttercup still feels too lowly for you, you might consider Clover, Daffodil, or Daisy.
Princess Buttercup, character in The PrincessBride
Buttercup, a crime fighting, super-human girl on "Powerpuff Girls"
Buttercup, The name of Prim's cat in The Hunger Games.
"Build Me Up, Buttercup," song by The Foundations