I love Marco Cantu's Fun Side of Delphi and C++Builder series during several Borland Conferences and CodeRage conferences. And now About.com launches a new contest on fancy Delphi applications.
Suddenly a virus written in Delphi which damages millions of Windows systems here in China comes into my mind too. It was written by another guy comes from my home town, the city of Wuhan. The virus is documented as Worm.Nimaya, so you can do a Google search to get more information about it. Yes, Delphi is powerful enough to build really horrible virus!
Please believe that you are only limited by your imagination no matter what programming languages you use.