We've commented many times on the record-setting hurricance season of 2005, but it continues to make news as yet another storm has been added to the list for the year, meaning that instead of 27 named storms for the year, there were actually 28. Here's where it gets a little confusing, though. However, the 28th storm has the rather awkward moniker of "Unnamed Subtropical Storm of 04-05 October 2005." Apparently, at the time the storm formed, a little south of the Azores, it was thought to be extratropical in nature, and only upon going over data from the region again during post-season reanalysis did the National Hurricane Center recognize that the storm did indeed acquire some tropical characteristics, enough so as to be designated subtropical. In this case, a subtropical storm with maximum sustained winds around 50 mph and a rather short lifespan.
An interesting tidbit from the Wikipedia entry on Subtropical Storms is that in 1972 the National Hurricane Center began calling these systems "neutercanes," intended to designate a type of storm that was intermediate, or neutral, between an extratropical and tropical system. Thankfully, that term was almost immediately discarded, and after using a variety of naming and numbering conventions when dealing with subtropical storms in the years since, NHC in 2002 began simply drawing numbers (for depressions) and names (for storms) from the same list as the fully tropical systems. That being the case, this storm would have been named "Tammy" had it been recognized as a named storm at the time it developed. The unnamed storm can be seen as the track numbered 19 (in the square white boxes) toward the upper right of this map from the NHC web site.