I remember being so happy about the gadget cards being printed in the TCG - seeing how Yugi's deck differed from Yami's in the anime was a true highlight in itself, but seeing some of those unique architypes as actual cards in the GX era proved especially exciting. Marshmallow and Golden Sarcophagus were also very welcome additions in my book.
Strike of Neos is one of my favourite sets from that era too, great to be reminded of how highly regarded it was at the time. I'd almost forgotten just how many great new architypes were introduced alongside the rapidly shifting meta, also: Six Samurai, Crystal Beasts, Gladiators and, my personal fav, Cloudians...