Mallory.
Melanie is cool and cute, but the "ie" is too girly IMO, and
Melody is girly and borderline trendy.
Mallory,
Melody,
Melanie (although I like them all)
Mallory: Long dark hair, fierce personality;
Melody: Light hair, cheery/peppy personality, maybe musical, popular;
Melanie: Brown hair, dreamy and cute personality
I actually can't think of any Melanies, Mallorys, or Melodys I know... I didn't realize I didn't know any though.
Melanie might be dated. Maybe the others are slightly, but I don't think any of them are too dated to use.