Tea isn't a huge thing for me, but if I had to pick one Sleepytime by Celestial Seasonings was the first tea I ever really loved, so it is most likely to be a favourite. Haven't tried the vanilla version yet, but looking forward to it.

Ingredients (original blend): chamomile, spearmint, lemongrass, tilia flowers, blackberry leaves, orange blossoms, hawthorne and rosebuds.

I find it relaxing in a way that makes me want to cuddle up with a blanket.
Plus it's the only one I keep in my pantry at all times, other than Throat Coat for when I'm feeling sick.

Another one I have right now that's good is Rest, by Tazo.

I found it when I was toying with the idea of making a dream pillow (filled with herbs and essential oils that encourage sleep/dreaming), turns out a bunch of the items I considered are in the tea so I was interested.

Ingredients: lemon balm, rose petals, honeybush, orange peel, lemon verbena, lemon peel, valerian root, licorice root, lavender, ginger, lemon essence oil, Chinese geranium oil, and "natural flavors" which is obscure enough to worry me a little...

It has this unusual smell that isn't easy to describe, but for some reason reminds me of the ocean..or potpourri intended to smell like the ocean rather? Oddly my first thought when I smelled it was of the seashells my great grandma used to keep in her home when I was a kid.

Its another good one for encouraging sleep, it's like a step up in potency from Sleepytime...for those particularly restless nights.

As for sweetening, I tend to only do it on gloomy or otherwise under the weather days. And always with honey.