Reddit mentions of Petco Dog Training Clicker, 2 in

I use this one, which is significantly quieter than the traditional box clicker like this one that you can find in any pet store. Now that my dog is older and isn't as fearful I find that I can use them interchangeably. I actually prefer the box clicker in certain environments (like outdoors or for more remote stuff) since the button clicker can sometimes be too soft.

If you have a dog that is scared or startled by the clicker, another good way to muffle it is wrapping it up in a sock. We had to start clicker training off like that at first to get her used to the sound being a good thing.

Buying a clicker would probably be better - having a loud clear sound is ideal - pen clicks are not that loud. Pens are great for young puppies or dogs afraid of a clicker, but if that is not a problem, a classic box style clicker is really cheap and really hard to confuse in their environment. Dogs are generally pretty good at determining what is a mark and what isn't but if you are around people who click pens around your dog a lot it COULD weaken the signal.

A clicker is also going to be loud enough to hear outside or in noisy environments (like training class). Many obedience school will give free clickers to students if you choose a school that uses positive reinforcement/clickers 8)

I'm sorry to hear about your experience.

I for one have a hard time snapping my fingers consistently. Jangling keys or a dog clicker make an excellent tool for safe-wording when gagged.

You could use something like a dog clicker driven by a servo or something.

http://www.amazon.com/Karen-i-Click-Training-Clicker-Clickers/dp/B002LAS2KW/ref=sr_1_2?ie=UTF8&qid=1404790777&sr=8-2&keywords=Dog+Clicker

http://www.amazon.com/Petco-PETCO-Dog-Training-Clicker/dp/B0006344B2/ref=sr_1_15?ie=UTF8&qid=1404790777&sr=8-15&keywords=Dog+Clicker

Any noise can be used as the "click," but something handheld will usually be more precise than anything verbal. Some other things you can use are saying, "yes!", the click of a pen, snap your fingers (only try this one if you've never snapped your fingers in an angry way to get his attention or something), a bottle cap (like a Snapple cap), and there might even be some sort of smartphone app you can download.

Are you using a box clicker? These can be pretty loud and jarring. You can try wrapping a towel over your clicker hand, or clicking in your pocket. They make some quieter clickers, like this one, but it's hard to say if it will still scare him.

Give the meds some time to get into his system, and don't be afraid to talk to your vet if you see no change. Just like with people, sometimes the first med doesn't work right.

That's interesting about the Kong. It sounds like he's lacking a ton of confidence. The clicker training should eventually help him become a bit more confident, and/or some day he might just "get it" and decide to try harder with the Kong. If it's really stressing him out, there are other puzzle toys you can try, or you can feed him exclusively through training sessions.

Hope that helps!