Hello everyone. This will be my first contribution to these community posts, since I am late to the workbook.
My favorite is the finger through palm, and I thank you Seeker for expanding on it... I'll be checking to see if I can feel my nail, the warmth, if my skin is going white, etc.
However, once I've become more accustomed to Lucid dreaming I am going to try to create my own personal reality checks. I believe that literally anything can be considered an RC if the user's belief and confidence is strong enough.
I had two specific self made RC in mind, and both involve a bracelet I'm always wearing. It was made by my dad a few years ago, and consists entirely of wire simillar to barb wire (obviously without the barbs). It was a custom to make bracelets of this style out of elephant hair (my dad and I are taxidermists, so we know all kinds of weird stuff about safari animals), but mine is the only one in the world that I know of that is made of metal. Although it is all one piece, it has little tabs at the top that when put together widen the bracelet's circumfrence, and when pulled apart tighten it.
Since this bracelet is very intimate to me, and I wear it all the time, even in sleep (only take it off for showers) these RCs should be effective for me. One of them was to look at my bracelet and make it glow. This is good because I can do it anytime during the day, no matter what I'm doing, and obviously if I can't make it glow I'm not dreaming. Another was just a personalized version of the finger through palm tech, in which I try to pull the bracelet off through my wrist.
I have decided to wait until I actually have LDs, using conventional RCs, before experimenting with creating RCs. But I do believe that they are not only possible, but more helpful than general techs that are applied to everyone.