My favorite type of hub to write is any type that I want to! I make a living writing for other people, going by their guidelines, writing within their niche... It gets so old and confining. I love to just log into HubPages and write whatever I have a mind to.
At the risk of sounding redundant, my favorite thing to write about is writing. It's a passion of mine since I can remember. It became my job about five years ago. It's amazing to find something that you love to do and get paid for it! It does turn it into more of a chore sometimes since jobs go hand in hand with finances which are synonymous with stress for me. But, I can just crank out a hub or two to refresh my brain.
Excellent question! Thank you for asking!