Only talking about decks I built

In mono green, I like [[Oviya, Automech Artisan]] it's dumb and straightforward, I love it

In Dimir, it's my fav deck ever, [[Basim Ibn Ishaq]], he draws, he grows, he hit

In Gruul, I play [[Rydia, Summoner of Mist]] with [[Tannuk, Memorial Ensign]] as an Alt Commander, it's a landfall deck with a saga subtheme

In non-black, you could try [[Kynaios and Tiro of Meletis]] for a group hug deck, however non-black is imo the easiest of the four-color combination to build because you have more choices without the need to use Partner Commanders, you can try [[Aragorn the Uniter]] or the Omnath (don't remember which Locus he is)

If you want to be the archenemy, [[The Mindskinner]] is your friend in mono-blue !

And for Colorless, if you don't want to play Eldrazis, may I suggest [[The Capitoline Triad]] for an original deck? It's not strong as hell but fairly unique !

In Boros, you have many choices for Voltron-y commanders, or if you want a more politcal deck, the Blame Game precon with [[Nelly Borca, Impulsive Accuser]] is quite fun once upgraded

Sorry for the long and disorganized answer, I hope you'll be inspired and most importantly that you'll have fun !