I personally find hunter to be the most fun in dungeons and pvp. It has a very high skill cap especially in pvp so there are always things to practice and get better at with the class. Additionally, hunter is always lots of action: pet micro, maintaining the perfect rotation, kiting, trapping, etc.
The only downside is that hunter even if played perfectly cannot compete for maximum damage in raids or even top 10 if you are in a competent raid. The same goes for pvp, big damage is not really a hunters strong suit, so your role is support from snares, cc, mana drains, flares, etc. A very very useful class in PVP despite the lack of damage though.