I just think knife kills are great, you just sneak up to the guy and put the knife to his throat.
This is ofcourse only if they know about knife kills, I wouldn't do it to someone who could freak out because they didn't know it
Cold Steel is the best training knife I have found so far. They make a few different versions and they are all around 10-15 bucks. I have had many others that were cheap and broke, but Cold Steel's are just molded rubber and really hard to break.