Revoice Pro - Revoice Pro is an audio plugin used for vocal tuning, time correction and ADR.
GSnap - With GSnap you can get an auto-tune effect.
n-Track Studio - Audio recording and music creation app for iOS.
Celemony Melodyne - Celemony Melodyne is the perfect quick and easy tool for all your tuning needs.
CrispyTuner - Fully featured vocal tuning suite.
MeldaProduction MAutoPitch - MAutoPitch is a full-fledged plugin by MeldaProduction that offers users precise auto pitch correction for vocals.