I can mention two that have allowed me to cut through the regular internet hearsay and trust my own experiences more:
Fender 150XL strings: Years ago, I tested different string gauges. I had grown up with the adage that heavier strings = better sound, but I just could not square that with what I was hearing. This set, which even had a lighter than usual thick E string (contrary to the light-heavy set mentality) seemed backward, but it had a clarity to it that I just did not find in heavier strings; the pure nickel gave them some extra warmness that I found to work well with the bright, clear amps I tend to prefer. Adjusting took some time, and I am almost relieved that the set went out of production, as I find that it is easier to keep the thick E string in tune with the 150L set. I still think that the thinner E string gave it something extra, but not enough that I am willing to start making custom sets.
TC Electronic G-System: Like most kids I started buying pedals early on. Some sounded good, yet I was never enamoured by the format, which seemed very convoluted if you wanted more than a couple of effects or if you wanted to use the FX loop at all. It took me years to even consider multi-effects, as I had grown up with the impression that they were little more than beginners' traps, but when I started to build my 'adult' guitar rig a few years back I gave them a second listen. Once I discovered the G-System, it all fell into place: you could get great effects without having to use stompboxes. As I started looking into stereo rigs, the advantages of high-end multi-fx only became more obvious. The system itself is getting somewhat antiquated, and I may replace it at some point*, but I would definitely look into a similar solution then.
*: I have an HX Effects that I use occasionally. It is newer and more advanced, but it is neither as sturdy nor as practical, not to mention that it just can't get it to sound as good to my ears.
