Over the years I think I have experienced most of the available (even if no longer available) X-10 modules, including the Leviton ones and the Radio Shack ones. I have a number that I consider my favorites.
I really like virtually all of the X-10 remotes, keyfob, credit card, palmpad and one or 2 others I cannot think the name of. Admittedly my discovery of them was in the Pre Alexa and Google days when voice control was yet to be realized, but I still find them useful, for controlling any of my controllable devices, including Z-wave ones.
Admittedly, part of what they worked so well for me was due in large part to the WGL572, an all code receiver with the ability to hook to an external antenna. No more multiple 751 receivers strategically placed around the house! Sadly the 572 is no more, but if you ever run across one for sale, BUY it!
I will restrict my likes to one per post, and, I think it is appropriate to point out other competing items in other systems that are also available where I find them as good as or potentially better than the older X-10 offerrings.
In that vein, I have started experimenting with a new offering called Yolink. Their products are well constructed and very fairly priced, but what I find most interesting about them is that they communicate through low frequency long range radio signals. Their range is supposedly 1/4 mile in open air.
They make a series of 4 key controllers, akin to some of the X-10 offerings. Their range obviates the need for the 572, and using EISY, I believe I can effectively turn them into any kind of controller I like, including an X-10 controller. I say believe because I ordered one to try out, and it should arrive next week. Reading up on it I think it will do exactly as I stated, but I will report back once I have one in hand.
Stay tuned I have several more favorites, some of which I suspect a number of folks might not be familiar with.