I started on a rebel 250. It was a little small but the island speed limit was 25 anyways, and there wasn't really enough room to get going too fast; well, there was one road, but I only got to go down that one once, and I managed to flog the 250 up to a screaming 65 mph.
My first big bike was a 919, and I'm not a crazy person by any stretch of the imagination so it was perfect for me.
'07 Ducati Monster S4RS
'06 Honda 919 (sold)
'95 Honda Rebel 250 (sold)