Have you ever tried to empty your recycle bin only to find one file is apparently still being used, and is stopping the process? Unfortunately OSX Finder doesn't tell you what's using the file.
Lock-UnMatic is a neat application that solves this issue. Drag a file, or files into the app's window, and you'll see what's going on. Lock-UnMatic shows you the path (location) of the file, plus what's using it, and which user.
If you don't have enough rights to rename or delete a file, Lock-UnMatic will unlock it, and if an app is using a file you want to delete, you can kill it.
Files can be added manually, and also added in bulk if you don't want to drag and drop them in. Preferences are pretty sparse, but you can choose whether to open the file list on startup, clear the list when adding new files, and also show the full path of files.