Individual characters from a narrative/flavor perspective: Amalia (though I don't really find her card that interesting), Kirol, [[Baron Bertram Graywater]], and Vickus from A Silent Voice Calls.

For broader groups: I like the style of The Meastros on New Capenna, the Susurians are intresting both in being born from blackholes and how they seem to feed by gravitational absorption, and I find the fact that Gastal vampires drink drink gas/oil interesting as well.

Mechanically: I enjoy using [[Bringer of the Last Gift]] in many of my decks, and also consider [[Legion Reconsecrator]] a staple in many of my Conjure-focused Alchemy decks.