Blue
Ravenous Bugblatter Beast of Traal
I suspect they're a lot more popular among active members of this community than in the D&D community generally
Everyone wants a bard in their party, just like everyone wants a primary healer in their party.
Which, as you point out, does not translate to everyone wanting to play a bard. Several of the standard buttons (big damage, high survivability, etc.) they don't push.