my friend has a free agent 16" called the lil hombre. when he messes around on that thing, its crazy. he has hit like curved wallrides, decent sized doubles, and drops(like 5 feet). that bike withstands a lot of abuse. but i still dont know how you would ride it, im like 5' 8" and always felt extremely uncomfortable and unstable on those damn things.
16" bikes are the best. I mess around on my sister's all the time. These guys built a pump course in a feild a while back near my house and left a bunch of beat little-kid bikes next to it, so I rode there once and had a blast riding.
To answer your question, there are lots of 16" bikes that can handle big people. 16" is a valid class in BMX racing too. This little kid I know has a Haro 16" BMX that cost around $100 and is burly. I'm 6', 170 and it's held up so far.