HATE WARRIORS? You've come to the right place.
Due to the huge swarm of warriors (both control and bomb) in the higher ranks, I decided to play this list and hit legend fairly easily on the Asian server (June 2019).
It's just a mashup between secrets hunter and mech hunter, and such concepts are by no means original.
The idea of this deck is to play your secrets and deathrattle minions in early-mid game, then start snowballing by using combos such as Necromechanic + Nine Lives, Mechanical Whelp + Fireworks Tech etc., and finishing off with Zul'jin and Da Undatakah in late game.
You have cards like Spider Bomb to ward off early threats and Zilliax to get you a lot of health when magnitized onto Mechanical Dragon or just any mech in general. Subject 9 helps thin your deck effectively (allowing you to draw your more important cards) if you draw it, but the deck still functions well even without having/drawing it. Marked Shot will sometimes give you an extra Nine Lives or Unleash the Beast. Zul'jin will give you a bunch of Wyverns and all your secrets, as well as some mechs on board and in your hand from Nine Lives, whileDa Undatakah gives you a bunch of 7/7s or destroys enemy minions when he dies.
Keep these if you have them almost all of the time.
Druid (Assuming Token archetype)
Hunter (Assuming Midrange/Mech archetypes)
Your role is to outlast their early aggression, since you always win the value game. Your Zul'jin is far better than theirs, and feel free to rely on Zilliax for some good heals. If you have the chance, combo Nine Lives with Necromechanic if you get to, since they don't have any means of countering 2 Mechanical Dragons.
Mage (Assuming Summoner archetype)
Try to rush them down before they get too many giants on board. Freezing Trap and Spider Bomb can help remove some giants. However, a good player would wait until they can combo said giant with Conjurer's Calling, and would not attack into a secret. This is why rushing them down helps. If they get a good Mana Cyclone turn early, don't be surprised if they win.
Paladin (Assuming Holy Wrath/Mech archetypes)
Rush them down before they can hit your face for 25 damage. If it so happens that they get to the last few cards, try keeping your health over 25 with the help of Zilliax and armor from Zul'jin. Push face damage while you can since they have what essentially is 2 free turns with Time Out!.
Priest (Assuming Chef Nomi archetype)
Kill them before they play Chef Nomi. This is a matchup where you should play Zul'jin earlier than usual, as long as he gives you a larger board advantage than anything else you can play. When playing SN1P-SN4P, choose carefully whether to magnetize or to play them separately, so you won't get punished by Wild Pyromancer and Silence.
Rogue (Assuming Lackeys/Pogo archetype)
Focus on making value trades and killing their minions with spells. Spider Bomb can be dropped alone on turn 3 to prevent your opponent from playing a huge Edwin VanCleef, but beware of Backstab. Some variants of Lackey Rogue run Chef Nomi, so consider going face if you have a board and health advantage. Similar to the Priest matchup, consider the possibility of Sap so you don't get punished by magnetizing everything you have.
Shaman (Assuming Aggro/Murloc archetypes)
What you want to do is to gain a board advantage so they don't burst you down with Bloodlust or gain too much value from The Storm Bringer. Focus on board presence and make value trades whenever possible. Don't hold back on a turn 3 SN1P-SN4P since the 4/5 total stats it provides can help you get on board early.
Warlock (Assuming Zoo archetype)
Warrior (Assuming Control/Bomb archetypes)
The game drags on really long, so focus on getting value plays (e.g. Mechanical Whelp + Fireworks Tech, Necromancer + Nine Lives) then win with you big boys Zul'jin and Da Undatakah. Keeping Mechanical Whelp in your starting hand greatly improves the consistency of the matchup since you'll be trying to make as many 7/7 Mechanical Dragons as you can. Also be wary of Supercollider and place your minions in accordance with Snake Trap and attack/health.
Keep: Secretkeeper (keep Snake Trap, Rat Trap or Freezing Trap if you have her already), Animal Companion, Spider Bomb, Ursatron and 1 Mechanical Whelp if you have enough early game. Houndmaster Shaw is optional here. Don't keep Zul'jin as you will want to play him as late as possible (i.e. after you have played your Nine Lives and Unleash the Beasts)
Subject 9: Replacing this card won't affect your gameplay too seriously.
These cards can be swapped out for second Unleash the Hounds (vs aggro), Unleash the Beast (vs midrange) or any secret of your choice (you can also consider Marked Shot). You can also swap out 1 Necromechanic, but a 4 mana 3/6 body with such a strong effect is almost always good.
I wouldn't recommend adding Sunreaver Spy to this deck, as it would make the deck rather inconsistent.
Please feel free to ask any questions in the comments, as well as suggest any modifications to improve this deck. Good luck laddering!