This is so hard to answer because I like so many different oolongs.
I love the se chung oolongs (Anxi oolongs other than tie guan yin); my two favorites in this category are huang jin gui / golden osmanthus, and fo shou / buddha's palm. I also like qi lan. I had a very dark wuyi qi lan which I liked too. I'm less a fan of ben shan, as it strikes me as a weaker / less interesting version of tie guan yin.
Where do I like them from? I've had good ones from different sources but right now my favorite source is Life in Teacup
I would like to get more into dan congs, and I'd like to explore more of the wuyi oolongs. I also would like to explore more Taiwanese oolongs; I recently discovered that I like Alishan oolong much more than dong ding, which was exciting. I still haven't settled on a good source of Taiwanese oolongs; a lot of the best ones I've tried have been gifts, and not labeled with an identifiable brand / source.