YCS Toronto was the first big event of the new format. Safe Bujins (which did nothing at the event), there was not a single "new" deck to be seen at this big event. But while there were no new decks, new cards were being used from both Number Hunters and Judgment of the Light. Some players might not have seen these cards in play yet, so let me point out their uses, one by one!
Mechquipped Angineer: This fairy XYZ is seeing play in both Mermails and Agent-style decks, but can also be used in Karakuri & Wind-up decks. In the last two mentioned decks, it focuses on battle position manipulation (and plussing because of that). In Agents it can be used (with two Venuses) to keep a boss monster alive (and it's the first Rank 3 fairy, which helps the Agent deck in general).
In mermails, however, it is used to keep Bahamut Shark alive. This combo is basically: Use 2 Lv. 4 monsters to summon Bahamut Shark. Detach 1 to special summon Abysstrite (in defense, obviously); then use 2 Lv. 3's to make Angineer. During your opponent's turn, ensure you detach one material from Angineer to keep Shark alive. Next turn, you can detach the other material to summon another Abysstrite. And Trite is both a wall and allows you to summon another Mermail from the grave when she's gone (a control combo).
Number 74: Master of Blades: Hyped due to it being a cheap rank 7; but it's also considered "less good" than Big Eye and Dracosack (it misses timing). But even with the (dis)hype, it saw a solid place in the extra deck of nearly every Dragon Ruler player, just in case.
Judgment of the Light - Effect Monsters
Archfiend Heiress: Used in Infernity decks: Searches out Palabyrinth and Infernity Archfiend. Consistency++!
World of Prophecy: The new boss monster of Prophecy decks: Upon its summon, it recycles 2 Spellbook cards and it can then optionally nuke the field (but no, this effect does NOT bypass Stardust Dragon).
Fencing Fire Ferret: Played in Dragon Rulers. Serves as a Ryko replacement. It destroys a card and deals burn damage. It's also a fire Attribute, which gives it a use in the grave (banish to summon Blaster).
Brotherhood of the Fire Fist - Rooster & Coach Soldier Wolfbark: Two of the key cards in current Fire Fist decks. Almost forgot to mention these two (lol). I did notice that Wolfbark is a more popular choice than Chick... Rooster.
The new mascot for the Fire Ferrets!
Judgment of the Light - Extra Deck Monsters
Mist Bird Clausolas: With the great number of Scapegoats running around, and with the easy combo of Effect Veiler + a Lv. 2 monster, this card is a very much welcomed addition to the extra deck. Its effect isn't half bad either.
Armades, Keeper of Boundaries: It’s a Lv. 5 synchro that can move between your opponent’s spells & traps. Sees more play than I initially thought it would.
HTS Psyhemuth: Saw play in Blackwings. It’s a D.D. Warrior lady on steroids and the best Lv. 6 synchro out there (as long as Vulcan the Divine isn't shipped yet).
Star Eater: Easy to summon it with synchro decks; hard to get rid of without the right cards.
Number 66: Master Key Beetle: The single most useful card of JOTL. It was seen in a large number of decks as a key protector.
Herald of Pure Light: Mainly used in both Prophecy decks and Agent-style decks. It's a perfect recycle-card for monsters. It helps dead cards to return to the deck and returns a monster from the grave to the hand.
Angel of Zera: A lv. 8 synchro that’s hard to get rid of (permanently), but has mixed results with the people playing it (Crimson Blader & Stardust Dragon are more preferred Lv. 8 synchro’s).
Judgment of the Light - Spells and traps
Transmodify: Thé hyped card of Judgment of the Light after the September F&L list was published. It works in Agent/Herald decks and it works in Infernities. Both people that topped with the Herald and Infernity deck had 3 of these (so yes, it works wonders).
Archfiend Palabyrinth: Used in Infernity Decks. Banish Heiress to get Infernity Necromancer; banish Stygian Street Patrol to get Infernity Archfiend and search a card (if your hand is empty). Like Heiress, it helps the consistency of the deck.
XYZ Encore: After the event, this is one of the card that became (over)hyped. Why? because nearly everybody in the top 32 played it in their side. And they all answered the question "why?" with the same answer: "To get rid of Evilswarm Ophion" (or Evilswarm in general). It's quick-play and your opponent cannot negate its effect (like how Super Polymerization works). I think Evilswarm players will now play Rank 3 XYZ as well, just in case (lol).