My preferred choice is a good Sheng Pu-erh though having a nice Shou Pu-erh has it's won merit. On second place are Japanese green teas especially Sencha with Genmaicha... The aftertaste is just so sweet.
You can never say no to good Oolong though.
The tea I dislike are the "Europe style" ones and in teabags.
I have some severe stomach issues atm, so all i can drink is herbal teas for medicinal purposes, but normally im addicted to black tea, especially english breakfast tea cream and sugar NOMNOMNOM, err slurp, slurp
I would definitely have to say that my fave is Gunpowder Tea also called Zhu-Cha something about it's earthy taste just makes me happy, and if you have it on a warm summers day while floating in a pool XD the best
Roob when I want something without caffiene in it (which is usually the case because I drink coffee otherwise), black tea if I don't care. Mate and oolong are also good.