As for food - Fazer chocolate when in Finland
A must trans-atlantic stop is Marks and Spencer to buy double cuff all coton dress shirts that don't cost an arm and a leg. They used to have stores in Canada (and Germany when flying through there), but they seem to have shut most of them (all of them in Canada).
The M&S website has been saying for three years that they will take international orders soon.
My friends in far off places usually ask me to bring peanut butter (Jif or Kraft)