How to format to FAT16

Put this into Terminal:
 
diskutil partitionDisk /Volumes/name x MBRFormat "MS-DOS FAT16" "newname" 2000M
 
where
name = name of the existing volume
x = number of partitions
newname = what you want to call the newly formatted drive
 
the 2000M at the end is the size of the partition, if it is the last, it will span to the end of the drive)
 
for instance:
diskutil partitionDisk /Volumes/UNTITLED 1 MBRFormat "MS-DOS FAT16" "WiiSD" 2000M
 
or
diskutil partitionDisk disk1 2 MBRFormat JournaledHFS+ OSX_HD 80G MS-DOS MEDIA_HD 300G Map