My favorite Mexican slang word is "chingar". It is so versatile. It can be a noun: Pasame la chingadera esa. Hand me that damn thing. It can be a verb: Como chingas. You bother me. It can be a destination: Vete a la chingada. Go to hell. It can mean a really good beating: Me dieron una chinga. Te dieron una chinga. It can mean getting screwed over by someone: Me chingaron. Te chingaron. And of course there is the ultimate "chinga tu madre" which involves someone's mother.
If James Lipton ever asks me what is my favorite cuss word, I will have no qualms answering that is hands down "chingar".