The machete seems to work just fine...
They can live well for around 5 to 7 years. As the years go by you may notice them having trouble doing normal rabbit things. You know your rabbit better than anyone. If the rabbit seems to be in pain, it most likely is. This is not a reason to end its life. But it is a reason to take to a vet. The vet will help answer your question.
Allow the rabbit to remain calm and still for a few minutes, gently stroking it's back. Then armed with a good rounded dowel or stick of about 40-50mm diameter, still stroking the rabbits back, gently push the rabbits ears slightly forward exposing the back of the neck. Then with a swift sharp blow to the back of the neck, this will kill the rabbit very quickly without stress or pain. The rabbit will instantly die but there will be a nerve reaction (the rabbit is not alive at this point) will follow with the rabbits rear legs bouncing for a few seconds.
What the heck IS WRONG WITH YOU? If you actually have to ask that question then you obviously shoudn't own a rabbit. And for goodness sake I hope you didn't try to do it yourself or listen to any of the turds that told you to get a vet to do it. They use common sense. If you need your rabbit to be out down because of an illness then I take all of the rude things I said back, but if it is because you no longer want it then I suggest you give it to your local pet shop. Good luck.
Shoot it with a 12 bore.
Take it to the vet who has permission to take in wild animals who will glad put it to sleep, don't be tempted to kill it yourself as you would probably make the animal suffer more by your amateurish efforts. Let the professionals do their job.
A blow to the back of the neck is the classic method.
Take a hammer and hit it's forehead with it real quick, but make it calm first and cover it's eyes.