There's Always One
Definition
The phrase "There's always one" refers to the single player in a League who has yet to click the green button to enter a event or Incarnate Trial. The reasons for not clicking may be due to lag, a bug, being AFK, or a number of other reasons. In any case, it keeps the rest of the league waiting for that single player, with irritated players griping "There's always one" in League chat.
It is believed to have originated from when Behavioral Adjustment Facility Trial and Lambda Sector Trial were introduced to the game, and simultaneously originating from all the servers independently of each other.
Derivative quotes change the number so it becomes "There's always two", if two people keep the league waiting, for example.
The quote was acknowledged by the Developers as it became part of the 2012 April Fools' Day joke.