This is a really interesting topic, lots of funny ideas :D
I'm eager to try those Lazav builds full of clunky creatures and that mirrorweave Kykar deck, as well as the pingers deck!
[mention]KitsuLeif[/mention] : I also had a Thromok deck back when it was released, I had so much fun with it. I remember a game where we were playing with the "secret target" variant: everyone had a secret player they needed to kill, and when they successfully killed them, they took over their "prey". I had a 81/81 Thromok on the board, equipped with a
Mage Slayer, which I used to attack and kill my current target. I then took their prey, killed the prey with
Soul's Fire, took the prey of the prey (which was the last player) and used
Fling right away, winning the game on the spot, without even leaving the declare attackers phase. :p
As for oddball-style decks, I usually tend to enforce theme over power. For example, I've built an all-creatures
Animar deck, a creatureless token
Narset deck, a
Riku deck with nothing but clones and fork effects, a color-changing deck with
Blind Seer. That last one didn't perform really well but I don't care about winning as long as I have fun. My next project is to build a
Rayami deck that aims to got all the keywords each game.
My current pet deck is a
Golos deck in which
every nonland card has a random effect (cascade, flip a coin, clash, explore, parley, polymorph, etc.) but I stayed away from typical "chaos" cards such as
Grip of Chaos or
Eye of the Storm in order to keep my friends. There is no direct library manipulation effect, save for
Orcish Librarian, which makes the deck really fun as you almost never know what's around the corner. Surprisingly, the deck holds rather well during gameplay as you can quickly flood the battlefield with permanents once the deck starts going. Special mention to
Primal Surge which is always a blast to cast and might just make you win the game... "might" (I still got 6 instants and sorceries in the deck).