Pretty much every druid spec except restoration.
I'll probably piss off all sorts of druids by saying this, but aside from resto, every single druid spec is a watered-down, less interesting version of another class and plays nearly the same. Why play Guardian if I could just be a warrior? Why Feral if I have a rogue? Why balance when I could be...well, any other caster?
I really don't get how people main this class. It's like a weaker muddle of a lot of other classes.
Honorable mention goes to combat rogues, enhancement shaman and demonology warlocks post-5.3.