it would appear that there might be some Americans who don't pronounce the second "f" in "fifth", so it would be more like "fith"

I can confirm that. I lived for three years in a community in western Michigan where *nobody* pronounced the second F in fifth (and they looked at you kind of funny if you did). The resulting pronunciation was *exactly* like "fith". The phenomenon, however, is not particularly widespread.

I am struggling to think of a genuine standardly-pronounced word with a silent f.

I don't think there are any, unless you count cases where the entire syllable containing the f is routinely omitted (e.g., camouflage). That's really not the same phenomenon as a silent letter.

Then again, several of the ones on the list aren't really the normal "silent letter" phenomenon either...

One that's omitted from the list is the T in tsunami, which has an entirely different linguistic background from the T in depot. Some of the ones on the list have examples that use other letters, e.g., the K in know is exactly the same as the G in gnostic, right down to coming from the same Indo-European root.

http://www.merriam-webster.com/dictionary/roman%20%C3%A0%20clef

Please learn how to make links on PerlMonks.

For dictionary definitions, the preferred form is [dict://roman a clef] ⇒ roman a clef, or alternatively [wikt://roman a clef] ⇒ roman a clef, unless you want one specific dictionary site in particular.

I reckon we are the only monastery ever to have a dungeon stuffed with 16,000 zombies.