So like, I've pretty much only every played Commander, and a little bit of Standard a while back (Shadows Over Innistrad / Kaladesh / Amonkhet era).

My favorite ever standard deck was MTGGoldfish's 5-color Panharmonicon deck because it was just so goofy. Regularly stabilized from <5 life to win games with that deck, it was very fun.

My favorite Commander deck has to be my Omnath, Locus of Rage deck. Been playing that boy basically since he came out and it just feels so good to throw a bunch of 5/5's around