I drink a lot of mint tea. I've got four different kinds of mint right now, but the best by far is still peppermint. I like to add a few slices of ginger (fresh or candied) and sometimes sugar or honey. Mint tea is the one beverage I can drink unsweetened without it feeling like a punishment.
Another drink I made last year that isn't exactly a tea: Fresh strawberry (or strawberry jam) and lemon basil steeped in
hot water, add honey and chill. I tried it with lemon balm too, but I'm not a fan of lemon balm to begin with.
Hibiscus and chamomile (either together or separately) are also nice cold.
Also not tea, but I use a lot of jam in
hot water to make flavored drinks. Just plop a couple spoonfuls in a pint jar, add hot water and lemon or lime juice to taste, drink cold or hot. Sometimes instead of jam I'll use dried fruit and some honey. Ginger, honey, and lime is also a favorite combo.
I've thrown a teabag into all of the above, too. Green for lighter and citrus flavors, black for deeper flavors like black raspberry, elderberry, etc. I try not to drink a lot of tea because caffeine can trigger panic attacks for me; decaf isn't really my thing, either.