Something which has annoyed me several times in VS2005 is that new classes are internal by default. I almost never want an internal class, so I went looking for the option to change. I never did find it, but a colleague has just pointed out the solution:
All new files come from various files in %InstallDir%/Common7/IDE/ItemTemplates
Find Class.zip and modify the class.cs file in this archive. Be sure to delete or modify the contents of the ItemTemplatesCache folder while you are at it.
*InstallDir is [Program Files/Microsoft Visual Studio 8] by default.