For The Sake of His Sorrowful Passion...

Shamelessly pinched from Faith & Family

...have mercy on us, and on the whole world!

Read all about the devotion here. Back in 2008, B16 said:
Mercy is in reality the core of the Evangelical message; it is the name of God itself, the face with which He revealed Himself in the Ancient Covenant and fully in Jesus Christ, incarnation of Creative and Redemptive Love.
I love the chaplet of Divine Mercy and have adopted the devotion, but I have to say I still think of today as Hunchback Sunday, just for my own amusement.