Had a hell of a time getting the USB thumb stick to show up in unetbootin on my mac - finally found this gem via the googles:
"I figured out if you rename the USB stick to FAT32 and format via Disk Utility to MS-DOS (FAT) with GUID scheme, the name shows up in unetbootin."
And that worked. Go figure. I had tried that format/scheme, but not with that name. Wacky.