Hwi Rola glad you've asked, there's soooo many ones I like from this TCG, probably the most of anys I've played/looked into
I'll list few
1) Currently, big fan of Abyss race, specifically its sub race- Abyss Royals https://duelmasters.fandom.com/wiki/Category:Abyss_Royale The protagonist of current era, Win, plays them! Their aesthetic, as well gameplay is sooo <3
2) Justice freak with one of "furigana free real estate" names https://duelmasters.fandom.com/wiki/I_Am_Justice_If_You_Want

3) Chaos Vi Na Shura is a design I think a lot about it's very neat dragon-like freak https://duelmasters.fandom.com/wiki/Chaos_Vi_Na_Shura
4) And if to go back to the roots, I like this fella :) Liquid People is one of my fav races as well https://duelmasters.fandom.com/wiki/Aqua_Hulcus
All that not to mention The dragons (Ryuusei, Katsudon/Katsuking, Dogiragon, Savark...)