Litwick, Lampent, and Chandelure are one of my favorite Gen 5 evolutionary lines. I guess I just like things that have a creepy vibe to them. Volcorona is another good new fire-type, especially for its signature attack which is basically a fire-type charge beam, only stronger.
Some older ones that I like include Flareon (along with the rest of the Eeveelutions), Moltres (along with the rest of the three legendary birds), and Blaziken.