The Druid who Soloed Onyxia seems to have become the Shot Heard Around the World. It was just Monday that WoW Insider brought you the video of Serennia of VANQUISH (Cho'gall, US) downing Onyxia. Today, as if challenged, tipsters sent in the video of a Paladin named Par (Khadgar, US), slaying the dragon by his lonesome. A few posts on the Official Forums have discussed the feat. It will be interesting to see if other classes step-up to claim solo Onyxia-credit in the next few weeks.
Thanks to everyone that sent this in!
Edit: There's some question about the original Onyxia Druid soloing - it wasn't Serennia the character, but Serennia the player (who is the Warrior of the same name). According to several commenters, it was Serennia playing on a druid's account. Also, the original Warcraft movie blurb is signed by Serennia of VANQUISH.