Above please observe Sensei Gordon Muller performing some "combat aikido" including gun and knife disarms and handcuffing techniques. He is excellent, and I love showing this kind of material to people who believe that "aikido doesn't work". I surely would not want to be on the receiving end of any of the techniques he does above, especially if he were not specifically trying to avoid injuring his partner (as he is in the video). I definitely would not want these applied on me when "excessive force" or other lawsuit risks did not apply (such as in a dark alley).
For aikido to work in a real life situation, against a determined, prepared (possibly armed) attacker, a few things need to happen:
1) YOU NEED TO BE FAST --- observe the blazing speed Sensei Muller uses and how he has no hesitation
2) YOU NEED TO BE PRECISE --- Sensei Muller is in exactly the right position, with the right grip at the right point
3) YOU NEED TO BE RELAXED --- tied to #1 above, there is no real speed without relaxation
4) YOU NEED TO BE COMMITTED --- Sensei follows through until the technique is over. No pause.
5) YOU NEED TO USE PSYCHOLOGY TO YOUR ADVANTAGE --- Sensei uses non-threatening body posture, hands-up genstures, and other means to set up his attacks.
6) MANIPULATION OF THE FINGERS HURTS (AND HELPS SUBMISSION)
7) PAIN (not injury) CAN BE AN IMPORTANT AID IN SUBDUING AN ATTACKER
Surely there will be naysayers and "what-if" ers as I would expect in every case. That said, I think Sensei Gordon Muller illustrates the kind of powerful, effective aikido that can be achieved with practice and strong intention.