I have always been amused by the concept of the cat leash. When I was growing up we had two cats and I couldn't picture taking them for walks. They didn't even like us to hold them for that long.
With that being said, I have known two cats who had owners that bought a cat leash with the intent taking the cats for walks. Owen bought Frank (that's the cat) a little harness and a leash. Frank was all for it. He would go outside and walk around and have a great time.
Sally, Victoria's black cat, was a different story. Now, Sally was a big kitty. She did not enjoy having the harness on, in fact, whenever you put it on her she would fall over and refuse to move at all. It was hilarious.
You know what else is hilarious? This video of a guy trying to put a leash on his cat. Now, I don't know why he starts off shirtless and in a towel, but watch it until the end (it is totally worth it).