Which file types should an upload script disallow?

I’m crafting a cliché file upload script and need some help creating a list of disallowed file types. I figure files such as .php and .asp could be a potentially hazardous to let people upload. What other files should I block? Any input is greatly appreciated.

I should note that the security of my server is all that I’m worried about, so blocking files such as .exe, which are only hazardous to the users which download them, are not of interest.