For the night of destiny (Lailatul Qadr)                                                                                                       

اَللَّهُمَّ اِنَّكَ عَفُوٌّ ، تُحِبُّ الْعَفْوَ فَاعْفُ عَنِّي

Allahumma innaka `afuwwun tuhibbul `afwa fa`fu `annee

O Allah You are The One Who forgives greatly, and loves to forgive, so forgive me

Ibn Majah: 3850, At-Tirmidhi: 3513