There is a very simple dua that is light on the tongue and very heavy in the balance on the Day of Judgement.

Dua:

Say ‘Subhan Allah Al-‘Azim’ and ‘Subhan Allah wa bihamdihi’

Hadith:

Narrated by Abu Hurairah: The Prophet (SAW) said, “There are two expressions which are very easy for the tongue to say, but they are very heavy in the balance and are very dear to The Beneficent (Allah), and they are, ‘Subhan Allah Al-‘Azim and ‘Subhan Allah wa bihamdihi.'” – Bukhari, Volume 8, Book 75, Number 415