[quote=Holmes]For some reason it really gets under my skin when I hear people call it a 'sangwich'. (Kind of like nails scraped across a chalkboard... Cringe.) Not entirely sure why.[/quote]

Me too! 
And I live in a city full of people that say it. I catch my husband once and awhile saying it, because he's a native Spanish speaker. I don't know why it influences the 'g' in the word sandwich.