Well...some may think it's cruel, but I slam their heads flat with the flat side of a big hammer.
Then I feed 'em to the cats so they don't go to waste, or add them to the composter. (usually a cat or raccoon gets 'em anyway)
Quicker than putting them in a container while they're freaking out, adding clove oil while they're freaking out, and then putting them in the freezer while they're freaking out, and shutting the freezer door and locking them in a dark cold room to die, while they're freaking out. :'(
If I'm going to play Goddess...I will kill quickly and mercifully. Not drag it out.