Trisana Chandler, or Tris for short is a walking talking example of Badass Bookworm at its best. A temperamental teen AND Fiery Redhead with a hot temper and the power to shoot lighting from her braids of hair.
Daja managing to contain a forest fire and preventing it from killing an entire caravan of people.
Earlier in the same book, she pulls off a social CMOA by demanding that the Trader caravan trade with her directly for her mutant magic tree. Daja isn't about to take being treated like crap just because she's an unclean Unperson.
Briar Moss. Knows street fighting and nerve points, and has plants that can rip you apart in seconds.
Particularly at the end of "Street Magic".
Sandry can manipulate magic as if it's thread, and does so to bind the magic and possibly souls of the four main characters together. Because she didn't know it was impossible.
An earlier and smaller example is when she uses her heritage to force her table-mates to accept Daja, culminating in her throwing a girl's comment of "If she's (Daja) a lady, I'm a cat" back in her face by taking a pitcher of milk and pouring it deliberately onto the girl's plate while saying "If I say my friend is a lady, then you had best start lapping, Kitty."
Dedicate Crane & co. saving the collective hides of pretty much all Summersea (and Winding Circle to boot) from a really nasty disease via application of magic and The Good Old Scientific Method. Crane may be a jerkass of epic proportions, but damn it, he's a brilliant one.
Evvy holding off a volcano in "Melting Stones" by convincing the fire spirits to put themselves into crystals.
The entire group breaking through a barrier meant to keep out invading armies and being held by the most powerful mage in Namorn.
Also from "Empress", Quen puts Briar and Daja in his shields and mocks them, saying that he doesn't really need to defend himself against plant and metal mages. Briar turns his magic into vines to find the holes in the spells, Daja turns hers into wires and supports them, and they wrap him up and strip him of his power.
From "Battle Magic":
Rosethorn going on The Quest to take the Treasures to the Temple of the Sealed Eye.
Evvy managing to lock away the knowledge that she's being tortured for, and then she fakes being dead well enough that it fools the soldiers and a very powerful mage.
By the time the good guys are done with Weishu, he needs a whole cart to take back every treaty and agreement he signed with the God-King.