Erm, maybe file based? JSON is the king if you count exchanges worldwide a sec. Maybe no 2 is form-data which is basically email multipart, and if course there's email as a format. Very common =)
JSON tabular data only adds a couple of brackets per line and at the start/end of the file vs CSV. In exchange for these bits (that basically disappear when compressed), you get a guaranteed standard formatting. Seems like a decent tradeoff to me.