Coolest project.... SharePoint sucks, so I wrote an app to extend it into something that is useful.

The app consists of:
- a custom SharePoint event receiver to maintain a custom retention setup
- a custom feature to enable users to tag documents as related to each other
- a custom search experience with custom views and previews
- a .Net windows service to sync the data into a SQL database
- a .Net MVC application to manage the reporting and notifications system
- a notifications system in .Net
- custom SharePoint approval workflow
- a PHP site that maintains a full backup of every document in the event that SharePoint goes down

I was the only developer on the entire project and while I asked for backup they never provided it. So if anything happens to me... And since I am a good dev, my code is self documenting and someone will need to telepathically link to me to find out the multiple places that all of this is running (like five different servers including both windows and Linux).

The whole thing, I have about 18 months invested into it ;)