HI BEN

Here is an easter egg on Regret with the words HI BEN on the ceiling

HOW TO FIND IT
You will need
 * A sniper or beam rifle
 * Sputnic Sputnic skull

Start the level Regret and proceed till you beat the drones and elites go to the outside and to your right you will see a temple with no bridge. Gernade jump there and go to the room to your right. Activate your flashlight and go to a left corner and snipe and you will see it.