Very versatile, is yarrow.
Yarrow (Achillea millefolium) is one of the most important medicinal herbs there is; it's found pretty much everywhere, and it's been used for everything.
Try this: pick up 5 herb books at random and write down all the different uses which they list for yarrow. Divide them into, say, ear/nose/throat, heart+circulation, digestive, liver, kidneys, urinary tract, lungs, reproductive, skin/mucosa, immune system, and see if there's any missing after you've done your list.
If yes, pick up another few herb books and see if that fills your list.
Yarrow has been used for everything because it works for everything, but it won't work wonders: if you have, say, menstrual cramps, it'll help long term. If you have urinary tract troubles it'll help - long term. If you have lung trouble it'll help - long term.
It has a number of different actions and a number of different constituents. It works a bit like Silybum, a bit like dandelion, a bit like Echinacea, a bit like thyme, a bit like chamomile ... it's very versatile.
And few (if any) of those books will mention the root, which is great for toothaches.
A great herb, is yarrow.