Three Mac models exist with USB, and no FireWire. These computers are supported by Mac OS X 10.3, but not 10.4. And I have them all: the original iMac, the original iBook, and the PowerBook G3 with a bronze keyboard and SCSI.
A later PowerBook G3/bronze keyboard was almost identical, but had FireWire and internal AirPort slot. There were a few different slight revisions of the iBook (I have the SE) and the iMac (Rev. B, which I have, and the "life savers" colored iMacs) model without FireWire.
Anyway, Apple screwed me here pretty good, if I cared about installing Tiger on these computers.