Sellotape
I don't know how this song isn't on the album. I guess you could argue that it's on the Folk the World cd, but then so is Bowie, Ladies of the World, etc.
Anyway, I think it may be my all time favorite Conchords song. Although if I think about it too hard, I might have to say Bus Driver's Song too. :)
Also really, really hot? The way Bret says "Voila -- le conversation a la parc" in Foux Da Fa Fa... I can listen to him say that over and over.