I've had mixed experience with Steel. Sometimes, despite its many resistances, one of my Steel Pokemon just won't have a talent for lasting very long in battle. But other times they're just plain awesome. I like Steel as a type overall, and I definitely hope to use more of it--especially now that it has a type advantage over Fairy to add to its usefulness. Picking a favorite is rather difficult, but I am absolutely loving my Aegislash right now...
Next up is Dragon.