This is a request for a feature which is not present in SSDT (at least the VS 2010 version), but is available in SSMS.
In the SSMS "Object Explorer" window, you can drag a list of all columns or parameters from a table/object and drop it in the query window, to quickly obtain a comma-separated listing of all the names. This feature is the quickest way that I've found to get such a list, and I use it when I need to copy a proc with many parameters, or to query a long list of columns from a given table.
The SSDT "SQL Server Object Explorer" object explorer window is functionally similar to the SSMS "Object Explorer", but doesn't seem to support dragging any object or child objects to the code window. The one amendment I'd like to see, compared to SSMS functionality, is that the list of columns should be bracketed.