Not a tea connoisseur, but you might consider giving genmaicha a try. It's a green tea with toasted rice kernels in it that give it a fairly unique taste.
Gunpowder green tea I use when I make Moroccan Mint tea, which is pretty rare these days. Gunpowder tea + fresh mint leaves + lots of sugar.
I'm currently working through a container of Long Jing (also known as Dragon Well), a Chinese green tea. It's from the same region my girlfriend was born in. Supposedly it's one of the more famous Chinese teas, but she doesn't think much of it, I guess because they serve it everyday tea there so it's nothing special to her.
That's about all I know about green teas. I've tried a lot though.
Black teas, I don't really know much. I had some great tea in England, it was actually nice and strong and flavorful, instead of the watered down stuff you get over here.
Oh, and sweet tea. Luzianne sweet tea with lots of sugar.