Components to avoid in Delphi

Anything for which you don't have the source. Nothing says "frustrate me" more than not being able to figure out why a component is behaving the way it is because it's poorly documented and being stuck on an old Delphi version because I can't recompile it.

Anything you don't absolutely need.

I am currently maintaining a large application that is dependent on a variety of 3rd party components. In order to upgrade the application, you need to upgrade the components. In the case of vendors that are no longer in business, that's a problem. As a result the entire application is stuck in limbo.