What are the adhkar (remembrances) and du'as (supplications) that strengthen faith?

The believer should strengthen his faith by increasing acts of obedience and remembrance [of Allah], for faith increases with them and decreases with sins. A Muslim asks his Lord to renew faith in his heart, for the Messenger of Allah, peace and blessings be upon him, said: "Indeed, faith wears out in the interior of one of you, just as a garment wears out, so ask Allah Almighty to renew faith in your hearts." Among the supplications that help to solidify faith are: "O Allah, O Controller of hearts, direct my heart to Your obedience," and "O Turner of hearts, make my heart firm upon Your religion," and "O Allah, I ask You for steadfastness in the matter, and determination in guidance."