I'd probably use Ghost (they are badASS) or Steel types...They are my two favorite types.
I'd be Steel for Elite four
And Ghost for Gym Leader. I'd be later in the game, like 6th or 7th
Lampent (with Eviolite, I've always thought Lampent was cooler than Chandelure)
Marowak (LOLOLOLOL I suck)
Stantler. (PM me if you want to know, for I'll probably start ranting)