I grew up in the Southern states, so I had a LOT of iced black tea growing up--loaded with sugar, as is the traditional Southern way. A couple of years ago I weaned myself off of sweet tea and haven't put any sweeteners in it since. It's so much tastier that way! As for hot tea, I usually favour black (specifically Earl Grey, Lady Grey, Irish or English Breakfast), peppermint, or subtle herbal teas like Celestial Seasonings' Sleepytime blend.
I used to work for Starbucks, and part of being a barista is tasting everything the store sells; the pastry case was not so kind to my waistline, but trying all the different teas was a great adventure. Turns out there are a lot of unusual elements of teas that taste fantastic--passion flower, lemon grass, rooibos, stuff like that. I never really got into the white teas, as there was so little flavour it seemed like I was just drinking hot water--maybe it's better cold?
Now that the summer weather has amped up I like to cold-brew black and peppermint herbal teas together in a jar of water in the fridge, it only takes a couple of hours and it's really refreshing, not bitter like some tea can turn out of you hot-brew it and then ice it. Aside from mint, herbal fruit teas like lemon and raspberry, or flower-based ones like hibiscus and vanilla, are also great to add to black or green tea for a little more sweetness and flavour complexity.
Have you tried already-flavoured green teas, that incorporate things like dried fruit bits into the tea bags? I used to not like green tea much either, until I tried Republic of Tea's blueberry green tea. It's wonderful stuff, doesn't taste like grass at all, and that brand has other fruit flavours of green tea, like pomegranate. I've usually only been able to find it at places like Whole Foods and Trader Joe's, though a few independent grocers are bound to carry it. Mint green tea is also tasty, and easy to find. :)
Resist much, obey little. -Walt Whitman