During one of the breaks I get from DMing there was an interaction that went like this during a fight. We were 9th level.
DM: "Okay. The giants start coming your way."
Player of the Twilight Cleric: "Wait guys! I can grant everyone 1d6+9 temporary hit points that will refresh every round for the whole fight."
The rest of us: "Wow! That's awesome."
Me: "When did you get this ability?" - Note: we had been 9th level for a while.
Player of the Twilight Cleric: "Um. 2nd level."
Me: "So we could have been using that this whole time?"
Player of the Twilight Cleric: "Yes."
Me: