Pony Amnesia: Love and Mysteries

Pony Amnesia is a visual novel styled game that lets players take control of a pony that has awakened in the Everfree Forest without his or her memory. Confused, the amnesic pony makes his way out of the forest and finds himself in Ponyville, where everypony is preparing for the Summer Sun Celebration. Upon hearing his or her story, the ponies of Ponyville are quick to welcome the new stranger into their town and take care of him. However, strange events occur that keep hindering the preparations for the celebration. The new pony will have to team up with his friends to solve these problems as well as learn more about himself.

[From MLP Fan Labor Wiki]