Typically, it's lore/appearance for me; I usually find class choices I like after. The more otherworldly/unfamiliar in culture, appearance, etc the better. I really enjoy Pantheon's approach with gnomes and the skarr look incredibly interesting as a concept - I'm personally looking forward to playing them both.
Reading the lore of Dark Myr just sealed the deal right away. From creation of love and a glorious purpose to the anguish of our Lady Mother and twisting of our minds and bodies into cursed anthropomorphic beings.
Betting there is some badass underwater zones near Syronai, and expecting the Nythirian Red to dwell within, and to perhps have found some remaining breathable pockets of water from Nythir's sacrifice to live in, or like some have speculated are undead(which i think). High level zone for cousins of the master race.
Plus the Dark Myr look badass.
Ermos be cursed.
Archai Monk - to me there is a natually infinity towards this combo. I want to see how the elements playout in gameplay with the monk class and the Archai.
If this pans out in beta Monk will be my main.
Hafling Rogue - I find the Rogue reveal very intriguing on the utility side of things. Hafling is a natural stealth fit and would be fun to roleplay.
Dwarf Pally - Considering that Brasse is on board, how do I not do this? Really good chance this becomes my main. Especially because I like to role-play. I want to kick some undead ass.