Seriously, we wanted to keep our cats off of some of our furniture for the same reasons that you want to keep them off your car. My wife bought vibration-sensitive cat alarms called "Tattle Tale" that sit on the furniture and let out an ear-piercing tone with the slightest vibration. It came out of some catalogue, but pet stores may have it.
Just turn on the switch and put it on top of your car or on the hood. Toss your cat onto the car so that the alarm goes off and the sound will scare it away. Do that about three times, and you are done. If the cat tries to get on the car again it will be frightening and unpleasant. We have no more problems with our cats and our furniture.
I have used this product to train my own cats, and it seemed to work fairly well: http://www.epets.com/catscram.html I attached two suction cups to the bottom of the CatScram so I could stick it onto the cars surface.
I have also used a ScatMat: http://www.safepets.com/petmat.html which sends the equivalent of a static electricity shock to the paws. This might work better on a soft top, but I'm not sure it would survive getting wet.
So... anyway, to get the thread back on track... to kill a cat, poison is discreet, traps require less effort, but a high power rifle is much more sporting.
Ok, ok... only kidding. My GF has two cats, both of which are too fat to jump on anything, and they stay in the house anyways. i agree with Jenn, though... any animal out stray is the fault of the owner.
Take photos of the cat, especially if you can catch it in the act, and get photos of any damage the cat causes... CYA, just in case they do try to deny responsibility.
Was that foil used to cover the car while baking in the oven?
Sorry, the devil made me type this:evil: :evil:
As for getting to like cats, as posted in another thread, my wife is deathly allergic to cats (she been hospitalized a couple of times for it), so cats are not welcome around my house. We currently have a bit of a problem with some strays that live in the storm gutters, and like to hang around our front porch (in spite of our two dogs). I don't think my attitude is going to change...
cover the car and atop the cover place sheets of stuff like fly paper. a cat will definiitely not want to be on sticky surfaces. after it learns not to climb up you can go back to normal life with no fly paper. otherwise shoot the fvcker
actually there is an item sold by pet supply places called scat mat or some such thing. a 9v battery provides a tingling shock through a grid of wires. it deters irish wolfhounds and cats quite well. plastic sheet almost the size of an elise top. worked quite well for me to deter some cats.