If you want to get revenge on the Spanish Slug http://en.wikipedia.org/wiki/Spanish_slug, you can actually eat it (yuch!) According to http://www.aftenposten.no/nyheter/iriks/article2538243.ece you must
1) Put them in salt for 2 or 3 days.
2) Boil them in water for about 3 hours
3) Add taste, garlic, wine or butter
4) Enjoy!
Spanish Slug is know as the Iberiasneglen in Norway, or Brunsegl. The latin name is Arion lusitanicus.