Willow is one of the most powerful witches in Buffyverse. Or, at the very least, she grows up to be. Right now she's still working on that but, unlike the other Buffyverse characters, she has the raw magical talent to do the real bad-ass spells.
Right now her two perfect spells are disinviting vampires and resouling Angel. (According to canon, the disinvitation spell needs a proper witch, but a beginning witch is fine. Angel's curse, however, is a powerful spell and Willow's the only known person in Buffyverse who can do it.)
She also has telekinesis which she can use to move small objects (pencils, stakes) around with some accuracy, and I've had her practicing to show her gaining the ability that lets her move bigger stuff.
Canon-wise her magic so works at the speed of the plot, but she's got locator spells, she's worked on an instant-sunlight spell, she's got some fire-starting, and later on in canon she gets things like teleportation spells into the mix as well as telepathy.
There are also more powerful magics that she uses in later seasons, but the implication is that she got them when she dipped into dark magic and her spells wouldn't have been the same if she'd stayed on the right path. OTOH in s7 there's the implication that she was always uber-powerful and just needed to know how to control her magic properly so... yeah. Though unlike before, I am playing her now with her spells working more often, since she's been practicing and researching. Just no dark veiny Willow type stuff. yet
Oh, and she's also known to hack spells to make them bigger, better, yellow, faster, different.
Re: Magic Abilities
Right now her two perfect spells are disinviting vampires and resouling Angel. (According to canon, the disinvitation spell needs a proper witch, but a beginning witch is fine. Angel's curse, however, is a powerful spell and Willow's the only known person in Buffyverse who can do it.)
She also has telekinesis which she can use to move small objects (pencils, stakes) around with some accuracy, and I've had her practicing to show her gaining the ability that lets her move bigger stuff.
Canon-wise her magic so works at the speed of the plot, but she's got locator spells, she's worked on an instant-sunlight spell, she's got some fire-starting, and later on in canon she gets things like teleportation spells into the mix as well as telepathy.
There are also more powerful magics that she uses in later seasons, but the implication is that she got them when she dipped into dark magic and her spells wouldn't have been the same if she'd stayed on the right path. OTOH in s7 there's the implication that she was always uber-powerful and just needed to know how to control her magic properly so... yeah. Though unlike before, I am playing her now with her spells working more often, since she's been practicing and researching. Just no dark veiny Willow type stuff. yet
Oh, and she's also known to hack spells to make them bigger, better, yellow, faster, different.