Twilight Sparkle is a cute witch. Have a fanfic about that, and a sequel to another below!
[Adventure][Comedy][Alternate Universe]
Author: Epsilon-Delta
Description: Seeking fame and fortune, Rainbow Dash sets out to defeat the legendary witch Twilight Sparkle and collect the five hundred million bit bounty on her head. The one thing she wasn't counting on was Twilight being less evil than she expected.
A Witch in Broad Daylight (New Part 36!)
[Alternate Universe][Adventure]
Author: cursedchords
Description: Equestria's history is a multicoloured and complex tapestry, speckled with the works of the great ponies of its past. But there are two dominant colours, visible everywhere, and they are the contributions of the two ponies who saw it all: Celestia and Luna. A comprehensive understanding of Equestria is impossible without first knowing their whole story: from its start, in the middle of Discord's Chaos, to its finish.
Celestia and Luna were born into a lawless world, just two alicorns trying desperately to survive. Little did they know the great destiny that fate had chosen for them. On the road to that destiny, they will discover everything that lay underneath the Equestria of old, and set the stage for all that came after.
Sun & Moon Act I: Ascending Star