In Japanese, the sign itself is called "attomaaku" ("at mark") but it's pronounced as "atto" when dictated. So someone's email would be johnsmith-at-gmail-dot-com, and if you ask a Japanese person to pronounce the symbol, they would say "atto". However, if you show them the symbol and ask them _what it is_, they probably would say "attomaaku".
Semiotics is fascinating.