I haven't been to any real bad places(Besides Paramore Street in Orlando, Florida. Probably the most ghetto place Ive seen besides inland Daytona Beach. I remember hearing some gun shots one time while I was in Daytona, too), though my dad once had to go to Atlanta, Georgia for a business trip, ended up getting lost and having to go through the seedier parts of town around 1 A.M looking for a hotel, had no car or anything and almost got mugged.
Definately crosses off Atlanta from my 'Places to visit while I still live' list.
Jakarta was pretty scary when I was there, I've been to some rather rough parts of Miami as well. Then of course there's Torquay, where I brave the chance of getting stabbed pretty much every friday night.
A few more actually: St. Paul's in Bristol, Brixton in London, dodgy parts of Soho - also London, Moss Side in Manchester and quite a few rough areas of Liverpool.