Terz's comment on my post has reminded of our speculations on Sith Lord naming conventions. Following the pattern of Darth (in)Vader and Darth (in)Sidious, we posited quite a few hypothetical Sith Lords who probably didn't make the cut, for very good reasons - like Darth Sipid, and Darth Continent.
Predictably, as with all graat ideas, someone's already done it. You can see the reductio ad absurdum of the Darth+(in) naming convention at this page. My favourites include:
Darth Cest (a good candidate for Luke's Sith name, had he and Leia continued in their loving ways)
Darth Bred (the logical conclusion from above)
Darth Competent (probably killed himself with his lightsaber during training)
Darth Vigilate (strides up and down examination halls, breathing heavily)
Darth Dex (the last Darth)