Many people who have little or no background or experience with Polish or other Slavic languages have trouble pronouncing my last name: "Szczepanczyk".
If you read the International Phonetic Alphabet, I pronounce my last name as follows:
but the crude pronunciation guide I sometimes offer in emails renders my last name as [shchih-PINE-chick], and it is very often the first syllable -- indeed, the front of the syllable, or what phoneticians term the syllable "onset" -- which flummoxes most people.
"sz" in Polish is pronounced like the "sh" sound in English words like "shirt" and "shoes". "cz" in Polish is prounced like the "ch" sound in English words like "cheese" and "chicken".
This fricative-affricate sound sequence ("sh" followed immediately by "ch") can occur in English -- for example, in the phrase "fresh cheese". But the key difference there is that the sound sequence occurs across words, rather than in a single word or, as is the case with my last name, in a single syllable onset.
If you'd like to hear the pronunciation firsthand, here is an MP3 audio file where I pronounce my last name twice.