The registration and protection as trade mark of single letters is a hot topic (see the AG's opinion on the "alpha for alcohol" appeal, on Class46 here).
Gillette sought to register the stylized "G" depicted left for a variety of goods, e.g. perfume, soap, and razors. The Swiss IPO refused, citing lack of distinctiveness.
The Swiss practice regarding registration of single letters and numbers is in principle very similar to the OHIM's practice, the Swiss IPO will refuse registration of unadorned single letters on the grounds that such letters are devoid of distinctiveness, but will register letters or numbers if they are sufficiently stylised so that the overall graphic impression created is distinctive. The question for the practitioner is, of course, when is a letter stylized enough to pass the test?
Well, in this case, the letter failed the test. The Federal Administrative sided with the IPO and held that the styling of the letter was not very unusual or memorable, but rather a minor variation of a standard letter and the sign overall lacked distinctiveness (Gillette did not (yet) rely on acquired distinctiveness).
The case (PDF, German) is technically not final, it can be appealed to the Supreme Court.