I've used Collections.emptyList for methods that return a list but that are called with arguments that don't make sense.
For instance a stream processing application where you want to access different parts of the stream, perhaps based on dates. You query for a time span of items from the stream but if there are no items in that time span you would return an empty list. Throwing an exception wouldn't make any sense since the isn't anything wrong with the query. Returning null also doesn't make much sense because then all the calling code needs to check for null.
Returning an immutable empty list allows the calling code the handle the return value nicely, you don't need to worry about threading issues since an immutable list is inherently thread safe.
