Re: My favorite silent English letter is:

[cjb]

I'm not sure about "f as in halfpenny".

That's a silent "lf" in English-English pronunciation.

[gregor42]

halfpenny did not work for me as well. Shall we go with giraffe ?

[mertserger]

Actually "halfpenny" works for me because the "l" is missing in the pronunciation of "half" anyway, so in English-English "halfpenny" only loses the "f" as there there was no "l" to lose. I would say something like "haaf" for "half" normally but "halfpenny" is like "haypenny".

"giraffe" has an "f" at the end when I say it. Can you say it without one? Wouldn't that just be "gira"?

[gregor42]

Concerning "giraffe":

I highlighted the second 'f' to indicate which letter was the silent one. This was an attempt to be consistent with other examples appearing on the list.

Source: "The final ⟨fe⟩ in giraffe gives a clue to the second-syllable stress, where *giraf might suggest initial-stress."

Concerning "halfpenny":

I was, admittedly, referring to the American-English pronunciation wherein I have yet to ever hear "hay-penny" but instead hear something closer to "haff-penny". Based on that experience the 'l' is dubiously silent.

I will not be lured into a test of yellow arcs regarding American vs. British usage of a commonly misunderstood language however. Let us instead both smirk at how odd we appear to each other & move on, enriched by the knowledge.

[mertserger]

Looking at the OED 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", but I am struggling to think of a genuine standardly-pronounced word with a silent f.