Standard
With the cancerous amount of times Guzma has won my opponent a game, and with weaknesses almost entirely determining match-ups (Volcanion auto-wins against any metal deck and Golisopod, any metal deck beats Gardevoir, etc.), I've been trying to find decks to play throughout this standard format, maybe figure out something more for the future when I attend another tournament or finally go to a national or a regional. Every now and then, I try to make Dusk Mane Necrozma-GX / Magnezone work and make it more consistent. I think a deck with the ability to OHKO pretty much anything regardless of weakness turn after turn has got to be something to pay attention to, and if I could just get through that consistency issue, that teny tiny problem, then one of the best decks in the format (I think) has been born.
Other decks I kind of play, Buzzwole / Garbodor seems simple and top tier, anything with a 4-4 line of Zoroark, rip through your deck making it 5 cards in just a couple of turns? Yes please! I was just playing Golisopod / Lurantis online, I don't usually play Golisopod since I like to play decks that can instantly remove a threat or OHKO, but combining it with the promo Lurantis (a bunch of copies) fixes that issue for me and makes Golisopod more of an energy-efficient threat, and I like that! And if I can make my precious Solgaleo-GX a tournament-destroying threat, so be it (at the very least, he's the most underrated card in the entire format as of the timing of this post, in my opinion).
Expanded
Not the format I tend to prefer between the two, but definitley can still be interesting from time to time. I currently have a Ninetales / Salazzle deck build in real life, and from online results let me tell ya, against every non-item lock deck, it sets up quickly and utterly and brutally destroys big EX and GX-based decks. I could build Night March as well, given the budget and just how good that deck is in expanded even today.