Yes, it is actually, though that had not occurred to me before, since it shows up in some very common words, like fant ("boy") and in a lot of slang: ful ("completely", from the German voll), zafrkniti ("to mess up, screw, cause problems"), and of cours fukati (another borrowing from the Germanic languages) and its derivatives. But these are all borrowings (fant comes from the Romance infant, but most of the others are Germanisms) or, occasionally onomatopoeic forms (frfotati, for example, means "to flutter"). Historically, the Slavic languages did not have a separate "f" phoneme; the f-sound existed only as the devoiced allophone of the "v" phoneme. But Slovene, having lived in very close quarters with German (and Friulian) for some 14 centuries, has made "f" its own, although I guess, compared to the other letters, it is still somewhat rare. But then, the other 10-pointer, "ž" is a full-fledged Slavic phoneme and doesn't strike me as particularly rare either.
Thanks for the Scrabble counts, Froggy. That's very interesting!
Done: "Ab C. Defghi & Co." It's an open list, so please contribute as you can. (Milosrdenstvi, I'm looking forward to seeing the Georgian alphabet up there, and the Indonesian from Bilby, the Irish from Fox, etc.)