"Rumour Has It"/"Someone Like You"
The much-hyped 300th performance in the show's history didn't disappoint. While Glee is known for its clever mashups, it's only one of a handful where both songs come from the same artist. In this case, it was Adele's "Rumour Has It" and "Someone Like You." Bringing Mercedes and Santana together for these duets proved that Naya Rivera can hang with powerhouse Amber Riley.