My favorite words to say in various languages:  Esperanto:  insekoj, Portuguese:  liquidificador, German:  Flammenwerfer.  I'm not sure I have a favorite Spanish or English word.  Maybe the longest one for English:  antidisestablishmentarianism.  I'll have to think about Spanish.
@hobbsc my favorite english word is 'widdershins'
@jezra i'm adding that one to my vocabulary, thanks.  really going to confuse my son.