I once made an electric fence to keep off slugs and snails. Just two parallel lines of copper wire stapled to wood about a quarter of an inch apart connected to the poles of a 1.5v dry battery. Boy! - have you ever seen a gastropod jump! I suppose it's a bit like the mild shock you can feel when you put your tongue across the connections of a battery - but over a much larger percentage of the critter's body. Still it worked beautifully - and the AA battery lasted the whole year.

Of course it's quite satisfying to make a trap with a bit of stale beer in a bowl - at least they presumably die happy - although I reckon some of them get out for a pee two or three times before their demise.

A french friend of mine actually goes out early in the morning to catch snails - and then cooks them with garlic butter - he says they're tastier than the big ones which are sold for eating.