Long time Magic The Gathering player here with too many decks to get fully into (57).
I have a series of 2 colour hybrid decks inspired by the great cards printed in Shadowmoor Block. Each deck runs a playset of one of the Lieges (G/W Wiltleaf Liege for example). These decks are among the most fun casual decks for both single and multiplayer formats.
I absolutely love tribal decks and have created and re-worked a ton of them over the years. They include 5 colour Slivers, Elves (mana elves leading to coat of arms or Kamahl, Fist of Krosa as finishers), Rebels (Mirror Entity makes them extremely potent), Wizards, Treefolk.
I love Commander format and run several decks including Teferi, Hanna, Viscera, Kiki-Jiki, Gaddock-Teeg, Animar, Karador, Damia and Kemba.
Besides that I tend to have a deck for many of the archtypes of years past. A Morphling Blue counter snore fest deck. A brainless red burn vintage deck, Oath of Druids, Survival of the Fittest, Madness, Affinity, Tangle Wire/Stacks type deck, Tooth and Nail, Classic sac black, weenie white shadow so on and so on.
Currently my personal favorite go to deck is my Commander Kemba deck. It's by no means a great deck in terms of power...but it's always a lot of fun. Roughly 10 creatures with great evasion or equipment fetch capabilities, 15 removal spells, 10 acceleration and 20 equipment. It's my only deck to run 1 of each Sword of X and Y equipment among tons of other fun ones printed over the years.