The 100-Million B-Pengos shown was issued. The 1 Milliard B-Pengos was printed but never issued. There's what claims to be one of the latter currently on eBay.
And as long as I've got the scanner warmed up... And a somewhat lesser denomination, but think what you have to sell to use it...
Well, honestly I thought this thread was for US high denomination notes, but, since everyone else jumped in... 100 Billion drachma.