Cursed Seal of the Forbidden Spell is an excellent tech card for decks that don't like MST, although GKs need to watch out for Seal themeselves since having Necrovalley hit is nearly an automatic loss.
Also it's a bit early into the format but I thought I'd post how I'd like to see the format changed:
Forbidden:
Archlord Kristya (locks Special Summons, returns Honest, and doesn't die? It's way too good and easy as hell to get out in Agents)
Black Luster Soldier - Envoy of the Beginning (what the fuck were they thinking)
Gallis the Star Dragon - (Gallis FTK is retarded and I'd rather this be banned than Birdman)
Mind Control (broken card is broken. If it couldn't steal face-downs I wouldn't mind it so much)
Royal Tribute (poorly designed card and one of the most crippling first turn plays out there)
Trap Dustshoot (giving an advantage in information and knocking away things like Effect Veiler that could stop your set-up makes this card a bit too good imo)
Limited:
Book of Life (too much easy revival for Zombies atm)
Genex Ally Birdman (sets up a ton of combos, pairs beautifully with TG thanks to the new ruling (example: bounce TG'd Sangan, xyz, detach to the graveyard (note: NOT banish since it's material)))
Gold Sarcophagus (too good to let run around in a TG meta. I'd probably also be content with this being Semi-Limited)
Master Hyperion (just a little too fast and destructive to leave unlimited)
Mind Crush (don't you love it when somebody knocks out your Veilers before going for their OTK combo? yeah, me too. Gets even better in Dark World decks)
Tribe-Infecting Virus (not as strong as it once was, especially since most decks have a variety of types, especially when factoring in Synchros and Xyzs. I think this card would be fine at Limited.)
Semi-Limited
Goblin Zombie (too much searching asfsadfsa)
Mystical Space Typhoon (triple is kind of unnecessary)
Reborn Tengu (give it the malicious treatment)
Tour Guide From the Underworld (new ruling kind of neuters it, still a bit too easy to run though)
Ultimate Offering (swarm decks are made a bit too strong with this; maybe even needs to be Limited)