Israel Kamakawiwo'ole (aka "Bruddah Iz") may have single-handedly been responsible for the resurgence of the ukulele when his song "Somewhere Over The Rainbow" appeared in the ER episode where Mark Greene's character dies after a long battle with cancer.
Sadly, Iz died only a few years later due to complications from obesity (he once weighed in at 757 pounds). The dichotomy of the giant man and the tiny instrument was anything but a joke, however, as the beauty and lightness of his singing defied his stature.
Enough about the man, what about his uke?
Iz played a variety of ukes during his career, mostly concert and tenor sizes. He favored ukes from Kamaka and Martin. The ukulele he played for his famous hit was a vintage Martin Tenor ukulele, and unfortunately Martin no longer makes ukes in this size, so if you want one for your very own you'll either have to be rich, lucky, or both (I'm gonna go with both).
More important to his sound was his special tuning. Israel favored a low G tuning (meaning the G string was an octave lower than the standard ukulele tuning), and would actually swap strings to different positions (so, for example, put the E string where the C would be). No one seems sure of exactly what strings he used where, but the result is that reproducing his sound is likely to be difficult. Best to stick his some CDs.