In the Goblin's Gold, I remember a scene with Leon in the tavern!
In the poisoned Chalice, Merlin drinks from the cup.
In A Lesson in Vengeance, Arthur drinks from a poisoned cup as well.
In the Fires of Idirsholas, Morgana drinks from a poisoned bottle.
That's all that comes to my mind right now!
Answer 2:There's also the episode Gwaine, when there was that fight with the thugs.