The Jesus Prayer is well known. You just repeat it over and over and it becomes a mantra.
O Lord Jesus Christ, Son of God, have mercy on me, a sinner.
People pray it all the time, and sometimes they use their rosaries to count the prayers. I usually change the words to:
O Lord Jesus Christ, Son of God, have mercy on us sinners.
That's my preferred way to pray the Jesus prayer. Sometimes though, I feel moved to place a person's name in:
O Lord Jesus Christ, Son of God, have mercy on Paula, a sinner.
It's a quick way to pray for some one.